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LIBRARY OF CONGRESS. 



Chap.. Copyright No. 

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UNITED STATES OF AMERICA. 

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SECOND COPY, 
i6b9. 



WORKS OF DR. THURSTOiN. 



2 50 



Materials of Engineering. 

A work designed for Engineers, Students, and Artisans in Wood, Metal, and 
Stone. Also as a Text-Book in scientific schools, showing the properties 
of the subjects treated. Well illustrated. In three parts. 

Part I. The Non-Metallic Materials of Engineering and 
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With Measures in British and Metric Units, and Metric and Reduction 
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The Ores of Iron ; Methods of Reduction ; Manufacturing Processes ; Chemi- 
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Copper, Tin, Zinc, Lead, Antimony, Bismuth, Nickel, Aluminum, etc.; The 
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"As intimated above, this work will form one of the most complete 
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" We regard this as a most useful book for reference in its departments ; 
it should be in every engineer's XxhxdiXy:''— Mechanical E}igiiiee?-. 

Materials of Construction. 

A Text-book for Technical Schools, condensed from Thurston's " Materials 
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Stationary Steam-Engines. 

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OTHER WORK'S OF DR. THURSTON.. 

A Manual of the Steam-Engine. 

A Companion to the Manual of Steam-Boilers. By Prof. Robt. H. Thurs- 
ton. 2 vols. 8vo, cloth $12 OO 

Part I. History, Structure, and Theory. 

For Engineers and Technical Schools. (Advanced Courses.) Nearly iioo 
pages. Fourth edition, revised and enlarged. 8vo, cloth 7 50 

Part II. Design, Construction, and Operation. 

For Engineers and Technical Schools. (Special courses in Steam-Engineer- 
ing.) Nearly looo pages. Third edition, revised and enlarged. 8vo, cloth. 7 50 

Those ^n\\o desire an edition of this vs^ork in French (Demoulin's trans- 
lation) can obtain it at Baudry et Cie., Rue des Saints-Peres, 15, Paris. 

" We know of no other work on the steam-engine which fills the field which 
this work attempts, and it therefore will prove a valuable addition to any 
steam-engineer's library. It differs from other treatises by giving, in addi. 
tion to the thermo-dynamic treatment of the ideal steam-engine, with which 
the existing treatises are filled ad fiaiiseam, a similar treatise of the real 
engine." — Engineering and Alining Journal , Neiv York City. 

" In this important vv'ork the history of the steam-engine, its theory, prac- 
tice, and experimental working are set before us. The theory of the steam- 
engine is well treated, and in an interesting manner. The subject of cylinder 
condensation is treated at great length. The question of friction in engines 
is carefully handled, etc., etc. Taken as a whole, these volumes form a 
valuable work of reference for steam-engine students and engineers." — Engi- 
neering, Lo?idoft, England. 

" The hope with wiiich we concluded the notice of the first volume of this 
work has been realized, and our expectations in regard to the importance of 
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carried out, and we find in the book all that it is necessary to know about 
the de'signing, construction, and operation of engines ; about the choice of 
the model, the materials and the lubricants ; about engine and boiler trials ; 
about contracts. The volume, which closes with an original and important 
study of the financial problem involved in the construction of steam-engines, 
is necessary to constructors, useful to students, and constitutes a collection 
of matter independent of the first part, in which the theory is developed. 
The publication is a success ivorthy of all praise.'''' — Prof. Francesco Sini- 
G.AGLIA, Bollettino del Collegio degli Ingegneri ed Arcliitetti, Naples. 

Treatise on Friction and Lost Work in Machinery 
, and Mill Work. 

Containing an explanation of the Theory of Friction, and an account of the 
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trated. Svo, cloth ■■ 3 CK> 

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Development of the Philosophy of the Steam- 
Engine. 

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to be of great value to the specialist." — Public Opinion. 



OTHER WORKS OF DR. THURSTON. 

A Manual of the Steam- Boiler : Design, Construction, 
and Operation. 

Containing;: — History; Structure; Design — Materials: Strength and other 
Characteristics — Fuels and Combustion — Heat : Its Production, Measure- 
ment and Transfer; Efficiencies of Heating-Surfaces — Heat as Energy; 
Thermodynamics of the Boiler — Steam; Vaporization; Superheating; 
Condensation — Conditions Controlling Boiler-Design — Designing the 
Steam-Boiler — Accessories ; Settings ; Proportioning Chimneys — Construc- 
tion of Boilers — Specifications ; Contracts ; Inspection and Tests — Opera- 
tion and Care of Boilers — The Several Efficiencies of the Steam-Boiler — 
Steam-Boiler Trials — Steam-Boiler Explosions — Tables and Notes ; Sample 
Specifications, etc. ; Reports on Boiler-Trials. Fifth edition, revised. 8vo, 
879pages ^5 ^ 

Steam-Boiler Explosions in Theory and in PracticCa 

Containing Causes of — Preventives — Emergencies— Low Water — Conse- 
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etc., etc. With many illustrations, i2mo, cloth j ^q 

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with stsam-boilers, either in design or use." — Engineering News. 

A Hand-Boo.k of Engine and Boiler Trials, and the 
Use of the Indicator and the Prony Brake. 

Nearly 600 pages. Fourth edition, revised. 8vo, cloth 5 00 

(Published also in French, as translated by M. Roussel ; Paris, Baudry 
et Cie.) 

•• laken altogether, this book is one which every engineer will find of 
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ports, note-books, etc." — Railroad Gazette. 

Conversion Tables 

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' indispensable to Mechanics, Engineers, Students, and in fact all classes of 
people." —Mechanisal Neivs. 

Reflections on the Motive Power of Heat, 

And on Machines fitted to develop that Power. From the original French of N. 
L. S. Carnot. i2nio, cloth , 2 00 

From Mtms. Haton de la Goupilliere, Director of the Ecole Natiotiale 
Super ieiire des Mines de France., and President of La Societe d' Encourage- 
tnent pour P Industrie Nationale : 

"I have received the volume so kindly sent me, which contains the trans- 
lation of the work of Carnot. You have rendered tribute to the founder 
of the science of thermodynamics in a manner that will be appreciated by 
the whole French people." 

History of the Growth of the Steam-Engine. 

(Pub. by D. Appleton & Co. , N. Y.) i2mo, cloth I 75 

Heat as a Form of Energy. 

(Pub. by Houghton, Mifflin & Co., N. Y.) i2mo, cloth .... I 25 

Life of Robert Fulton. 

(Pub. by Dodd, Mead & Co., N. Y.) i2mo, cloth. ....................... 75 



The Publishers and the Author will be grateful to 
any of the readers of this volume who will kindly call 
their attention to any errors of omission or of commis- 
sion that they may find therein. It is intended to make 
our publications standard works of study and reference, 
and, to that end, the greatest accuracy is sought. It 
rarely happens that the early editions of works of any 
size are free from errors ; but it is the endeavor of the 
Publishers to have them removed immediately upon being 
discovered, and it is therefore desired that the Author 
may be aided in his task of revision, from time to time, 
by the kindly criticism of his readers. 

JOHN WILEY & SONS. 
53 East Tenth Stkeet. 



STATIONARY 

Steam Engines 

Simple and Compound; 



ESPECIALLY AS ADAPTED TO 



LIGHT AND POWER PLANTS. 



V 

By ROBERT H. THURSTON, A.M., LL.D., Dr.Eng'g, 

Formerly of the U.S.N. Engineer Corps ; Director of Sibley College, Cornell 

University ; Past President American Society Mechanical Engineers ; 

Member American Society Civil Engineers; American 

Institute Mining Engineers, Etc. 



SIXTH EDITION, 

REVISED WITH ADDITIONS, 

FIRST THOUSAND. 

NEW YORK- 
JOHN WILEY & SONS. 

London: CHAPMAN & HALL, Limited. 
1899. 






29401 



Copyright, 1883, ELECTRICIAN. 



Copyright, 1884, R. H. Thurston. 



Copyright, 1890, R. H. Thurston. 



Copyright, 1899, R. H. Thurston. 



TWO COPIES RECStVED, 



(^h^ 







MARIS 1899 



(K 



\ 






\^^ 



PREFACE TO THE FOURTH EDITION. 



THIS little book is composed of articles written by the 
author for the Electrical Engineer, supplemented by 
later revision, and by the addition of matter relating to the 
new multiple-cylinder engine, which had been origi- 
nally prepared for the lecture-room and subsequently pre- 
sented in abstract to the American Society of Mechanical 
Engineers. It had its origin in a request, by the editor of 
the periodical above mentioned, that the readers of that 
journal be given an account, in simple and concise but 
fairly complete form, of the various types of steam-engine 
in common use ; of the principles of their design ; the cir- 
cumstances determining their efficiencies and their economy 
of steam and fuel ; their various forms as usually built, and 
the best methods of insuring further improvement. 

In complying with this demand, it has been thought 
advisable to give a brief outline of the progress of discovery 
and invention, from the earliest days of application of steam 
to the production and utilization of mechanical energy ; to 
trace the steps which led up from the rude devices of 
Savery and Newcomen to the highest attainments of the 
engineer of to-day ; next, to exhibit the principles of 



IV PREFACE. 

economy in the efficient application, through the operation 
of the steam-engine, of heat-energy into mechanical power, 
by conversion of the one form of energy into the other, 
observing the causes and methods of waste and the means 
available for their reduction, if not for their extinction, in 
some directions ; and finally, to describe and illustrate the 
standard types of engine to-day in use, and the details, so 
far as may seem important, of their construction. 

The peculiar demands made upon the designing and 
constructing engineer in later years by the introduction 
of electric lighting, with its requirements of economical 
operation of machinery having very high speed of rotation 
and absolutely compelling exact regulation, has led to the 
invention of new forms of engine, and especially of new 
methods of steam distribution and regulation. This has 
resulted in the introduction, in turn, of a new class of 
engines, known to the profession and in the trade as 
"high-speed engines," which possess these essential quali- 
fications of great velocity of rotation, and of nicety of regu- 
lation in a superlative degree, and which have, by their 
sharp competition with the older types, in their turn com- 
pelled an unexampled improvement in the latter, in the 
endeavor, largely successful, to adapt them to the same pur- 
pose. Thus high speed, very perfect regulation and very 
smooth action at maximum speeds, have come to character- 
ize the steam-engine of the present time in far greater 
degree than ever before ; while modern systems of manu- 
facture and the extensive application of special tools, 
designed each for its special work, have reduced costs of 
production of this right arm of civilization to such an extent 



PREFACE. V 

as to insure a more rapid progress in the useful arts than 
has ever yet been seen.' 

This subject was deemed so important to the mechanical 
engineer and to all having anything to do with the remark- 
able expansion now occurring in the work of electric light- 
ing, and of the extension of the systems of application of 
power, through the use of electricity to the impulsion of 
street railway cars and to the machinery of the smaller 
industries (to the supply of power to small shops and estab- 
lishments), that it was considered probable that a philo- 
sophical account of the rise and progress of this now enor- 
mous industry of steam-engine construction, and especially 
of its product, would be likely to prove acceptable to many 
intelligent readers outside as well as within the profession. 
In this anticipation the publishers have not been disap- 
pointed, as the fact of the sale of rapidly succeeding edi- 
tions proves to their satisfaction as well as to that of the 
author. 

The latest addition to this little work is in a final chap- 
ter on the multiple engine and the principles of its design, 
construction, and operation in successful competition with 
the older forms. The importance of this new departure in 
the construction of small engines, for electric lighting and 
similar purposes, may be imagined when it is noted that in 
some cases, at least, the compounding of a well-known type 
of " high-speed " engine has reduced its consumption of 
fuel for similar sizes and work enormously, the simple 
using almost double the amount of steam and fuel, in the 
smaller sizes, demanded by the compounded engine of 
otherwise exactly similar design and construction. As is 



VI PREFACE. 



Stated in the text, the smaller the engine the greater is the 
original waste, the greater the margin for improvement, 
and the greater the gain to be anticipated by this change. 

The author has endeavored to do full justice to the vari- 
ous engines described, while carefully avoiding the expres« 
sion of merely personal opinion in reference to debatable 
points. 

For a more complete history of the development of the 
modern forms of steam engine, as well as for an account in 
considerable detail of their various construction, and for 
discussions of the scientific principles and the practice in 
steam engineering, the reader is referred to the larger 
works of the author : his Manuals of the Steam Engine, of 
the Steam Boiler, and of Engine and Boiler Trials. This 
little book is intended to present the briefest possible sum- 
mary of the subject in popular form. 



PREFACE TO THE SIXTH EDITION. 



TN the preparation of the sixth edition of this little work, 
-■- the Author has taken advantage of the opportunity to 
incorporate a large amount of new material, the introduc- 
tion of which in a new chapter gives illustration of the 
rapid and important developments of even the short period 
which has intervened since the publication of the preceding 
edition. The general introduction of the direct-connected 
steam-engine, with its attached generator, has been a step 
in advance, in certain departments of construction and 
application, in practice, which has been, in a way, paralleled 
by the progress made in the analysis and development of 
the calorimetric and dynamic flow of energy through the 
machine, as a matter of applied science. Both these de- 
velopments illustrate admirably the extent to which the 
work of the engineer is coming to be scientific and theo- 
retically exact. 

Every steam-engine, like all other forms of machinery, 
may be said to consist of an ideal, theoretically perfect, 
apparatus overlaid by faults and embarrassed in its opera- 
tion by the impeding interaction of conflicting natural, 
physical, laws. The art of improving is that of elevating 



Vlll PREFA CE. 

the ideal, and of pruning away the defects of the actual, 
practical, construction. The ideal, purely thermodynamic, 
heat-engine has now come to be clearly and accurately dis- 
tinguished within the faulty actual machine. It has been, 
knowingly or unknowingly, steadily improved since the days 
of Watt, and earlier, and the best modern practice brings 
us to a construction of the real engine, which consists of 
about two-thirds ideal and one-third real, practical, defect. 
The method of discriminating between the limiting and 
" perfect " engine, revealed by Carnot and by Rankine and 
Clausius, is now so far itself perfected to permit the magni- 
tude and nature of all the defects of the steam-engine to 
be determined, and this " calorimetric analysis," originally 
due to Hirn and later brought into practical employment 
in the scientific work of the engineer, is exemplified by the 
several cases which have been imported into the sixth 
edition of this book. 

The practical construction and performance of the ma- 
chine, in its latest forms, may be studied in the text, and 
its illustrations, in the now newly inserted pages, and the 
various systems of direct-connection, and of engine-con- 
struction appropriate to them, as exhibited in the standard 
practice of the leading builders, constitute the essential 
and important recent improvements here described. They 
have been brought into the new edition as fully as the 
originally intended scope and character of the publication 
permitted. For the algebraic theory and mathematical 
physics of the subject the reader is referred to the works 
appropriated to that somewhat abstruse branch of applied 
mechanics. 



PREFA CE. IX 

On reviewing the whole history of the engine to date, it 
Avill be seen that progress continues in the directions al- 
ready pointed out and towards still higher steam-pressures, 
higher speeds of piston and of rotation, increased ratios of 
expansion in multiple-cylinder engines, and with constant 
reduction of the now^ well-understood waste which distin- 
guish the real from the ideal steam-engine. 

The Publishers have, in this edition, effected a great im- 
provement in the matter of book-making, by enlarging its 
page ; securing thus broader margins and a vastly more 
satisfactory volume both to the eye and to the hand. 
They unite with the Author in cordially acknowledging a 
real indebtedness to those engineers, engine-builders, and 
"business firms who have so liberally and promptly aided 
them in the endeavor to make the sixth edition of this work 
thoroughly modern, by supplying all information sought 
from them, and in so many ways facilitating the work of 
effective revision and extension. It is also a pleasure, as 
well as a duty, on the part of both Author and Publishers, 
to make hearty acknowledgment of their debt to that class 
of readers, extensive and evidently appreciative, if not 
always claiming to rank as mathematicians or men of sci- 
ence, v/ho find sufficient instruction and enough of interest 
in a semi-popular work of this character to call for six 
editions in so short a period. It is hoped that equal satis- 
faction may be given in subsequent editions — if they should 
Le called for during the remaining years of the life of the 
steam-engine in the character of man's greatest and grandest 
aid in energy-transformation for useful purposes. 

February, 1899. 



CONTENTS. 



ART. PAGE 
I. — Historical Development of the Steam Engine 3 

II. — Principles of Economy ; Special requirements 9 

III. — Engines indirectly connected. 

The Corliss Engine 17 

The Wheelock Engine 32 

The Greene Engine ^6 

IV. — Engines capable of direct connection. 

The Porter-Allen Engine 52 

" Buckeye " and Hartford Engines 6g 

The Cummer Engine 82 

The " Straight-Line " Engine 97 

The Armington & Sims Engine 116 

v.— Fast Engines of peculiar design. 

The Ball Engine 136 

The Ide Engine 148 

N. Y. Safety Steam Power Co ..............155 

Ericsson and Westinghouse Engines 162 

xi 



CONTENTS. 



ART. PAGE 

VI. — Latest Changes; Multiple-cylinder Engines ; Proportions. .177 

Compound Corliss Engine 199 

Cross-conn pound Engine 201 

Compounding Simple Engine 204 

Compounding-engine Types 206 

Multiple-cylinder Diagram 223 

Proportions of Parts 230 

Efficiency and Economy 235 

Distribution of Energy •243 

Financial Conditions 254 

Performance under Test 256 

Hirn's Analysis 260 

Power Table 264 

VII. — Direct-connected Engines ; Stations. 

Direct-connected Engines .267 

Steam-turbines 273 

Light- and Power-stations 286 

Development of Systems 287 

Efficiency of Stations 292 

Costs of Power-distribution 303 

Wire-rope Transmission . . 306 

Water-pressure Transmission 306 

Compressed-air Transmission., , 307 

Electric Transmission 307 

Behringer's Comparison 309 

Costs of Construction 315 

Organization 318 



Steam Engines 

FOR ELECTRIC LIGHTING PLANTS. 



I. 

Historical— The Development of the Steam Engine. 

THE growth of the steam engine into the forms now 
fairiHar to everyone who takes the slightest interest 
in this most important of modern mechanisms, has occurred 
by a series of transitions which is easily traced, and which 
is especially interesting to every thoughtful mechanic as 
representing the steps in a steady progression, toward ideal 
perfection, of which the end is not yet seen. 

A century ago, James Watt had just begun to introduce 
the first engines belonging to a, then, new type.^ A century 
before (1698), the ingenuity and practical skill of Captain 
Savery, had conferred an enormous benefit upon the mining 
industries, and through them upon the world, by applying 
the " fire engine " of the Marquis of Worcester to raising 
water from the then rapidly deepening mines. ^ Savery used 
steam of 8 to 10 atmospheres (120 to 150 pounds) total 
pressure, in some cases, and he is entitled to fame as the first to 
introduce that now familiar concomitant of civilization, the 

1. History of the Growth of the Steam Engine. International Series. N. Y"., 
D. Appleton & Co. 

2. Consult Manual of the Steam Engine, Vol. I., Chap. I., for more of detail 
relating to the history of the subject. 



STEAM ENGINES FOR 



Steam boiler explosion. The usual pressure was 3 atmos- 
pheres. These engines demanded about 30 pounds of coal, 
per horse-power per hour, as a minimum. The apparatus 
of Savery was not what would to-day be called a steam 
engine, at all. It was not a train of mechanism, involving 
moving parts, cylinder, piston, crank and fly-wheel, but 
either a single pair of closed vessels, or three vessels, one of 
which was a boiler, and the other, or others, metal chambers 
of spherical, cylindrical, or ellipsoidal form, which were at 
once condensers and pumps. The latter were filled with 
steam, which being condensed, the water rose into, and 
filled them, and was then forced out by a succeeding charge 
of steam, of pressure exceeding that of the head against 
which the lift took place. Huyghens (1680), and Papin 
(1690), proposed true engines with steam pistons traversing 
their cylinders, and forming, on the whole, much such a 
train of mechanism as is now so well known^ ; but the 
Newcomen engine was the first of this type to come into 
practical use. This machine, then called the " Atmospheric 
Steam Engine," consisted of a steam cylinder, with a piston 
taking steam beneath, the upper end of the cylinder being 
open to the atmosphere, the piston actuating a " working 
beam," or "walking beam," and, through the latter, work- 
ing pumps attached to the opposite end. Neither crank, 
shaft, nor fly-wheel was used ; the action of the engine was 
controlled entirely by the adjustment of its valves. In its 
operation, steam at a little higher than atmospheric pressure, 
was admitted below the piston ; the weight at the pump end 
depressed that extremity of the beam, raising the piston. 

3. Mem. Acad. Sci. Paris, 1680. Acta Eruditorum. LeipBic, 1690. 



ELECTRIC LIGHTING PLANTS. 



The steam below the piston was then condensed by a jet 
of water thrown into the cyhnder, producing a vacuum; and 
atmospheric pressure finally forced the piston down, rais- 
ing the pump-rod and plungers. The weight on the latter 
was adjusted to the work, so that, when steam was admitted, 
this weight should force the pumps to discharge the water. 
The only function of the steam was the displacement of the 
atmosphere, or counterbalancing it, by entering below the 
piston, and thus permitting the formation of a vacuum. A 
writer of that time states* that " Mr. Newcomen's invention 
of the fire engine, enabled us to sink our mines to twice the 
depth we could formerly do, by any other machinery "; but 
" every fire engine of magnitude consumes ;^3,ooo worth of 
coal per annum." The coal consumption was, at best, about 
20 pounds per hour and per horse-power. Smeaton, the 
greatest civil engineer of his time, put up many of these 
engines in Holland and elsewhere, as well as in Great 
Britain ; some were 66 inches in diameter of cylinder, and 
8 to 9 feet stroke of piston. It was this engine that Watt 
found in operation, when he entered upon the stage. 

Watt was not simply a mechanic ; he was a real philoso- 
pher, and a truly scientific investigator. A model New- 
comen engine, having been brought to him to be repaired, 
he took advantage of the opportunity to study the principles 
of its construction, to ascertain its defects, and to devise 
proper remedies. He found that the sources of loss were 
the conductivity, and radiating power of the steam cylinder, 
the alternate heating and cooling of the metal at each stroke, 
the imperfect vacuum, and the wastes from boiler and 

4. Mineralogia Cornttbiensis. Price. 1778. Appendix. 



STEAM ENGINES FOR 



Steam pipes. To correct these defects, he clothed his 
boilers and steam pipes with non-conductors, sometimes 
even making boiler shells of wood. Smeaton had already 
covered the pistons and cylinder heads with wood. Watt 
made a small wooden steam cylinder, and obtained great 
economy ; he made a more practicable improvement, how- 
ever, when he devised the steam jacket. ,He attached a 
separate condenser to prevent the loss due to the introduc- 
tion of condensing water into the steam cylinder, closed the 
cylinder at the top, made the engine double-acting, and 
finally adapted the engine to drive machinery, fitting it with 
shaft and fly-wheel, throttle valve, and governor, and thus 
making the steam engine such as we see it to-day, in all es- 
sential particulars, not excepting the steam jacket, and the 
arrangement of its valve gear to secure economy by the 
expansion of the steam. His engine was substantially com- 
plete by the year 1784.° 

Later changes have been a succession of refinements, 
and of developments in application. Stephenson, and his 
contemporaries, applied steam on railroads ; Stevens, Fitch, 
and Evans, and, finally, Fulton, in the United States, and 
Bell and others, in Europe, introduced steam navigation ; 
Sickels invented the " detachable " cut-off valve gear ; 
Corliss introduced the peculiar type of engine that has 
given him a world-wide fame, and so attached its governor as 
to determine the point of cut-off automatically, and thus to 
regulate the engine ; and, a little earlier, Robert L. and 
Francis B. Stevens designed the American river steamboat, 
and its beam engine, with so simple and effective a valve 

5. History of the Growth of the Steam Engine. P. 119. Farey on St. Engine. 



ELECTRIC LIGHTING PLANTS. 



gear that it remains, to-day, still standard. The compound 
engine, even, was brought oat by contemporaries of Watt, 
and thus every prominent feature and essential detail of 
the modern steam engine was introduced at, or before, the 
middle of the nineteenth century. 

Yet, practice has been steadily changing during the cen- 
tury, and the form and proportions of the steam engine, and 
the methods of steam distribution, have been undergoing 
constant changes. In the time of Watt, steam was worked 
at about 7 pounds pressure, per square inch, in stationary 
engines; they were always fitted with condenser and air- 
pump, and were slow in movement, and were, consequently, 
of small power in proportion to their size; they wasted heat 
and fuel to such an extent, as to demand 6 or 8 pounds of 
coal per horse-power and per hour. It is true that Wolff, 
in 1804, expanded 6 or 8 times, using higher steam and ob- 
tained the horse-power with 4 pounds of fuel per hour, and 
that John Stevens and Oliver Evans, in the United States, 
and Trevithick, in Great Britain, had already used still 
higher steam in non-condensing engines; but these examples 
simply illustrated the fact, now familiar to every student of 
philosophical history, as pictured by Draper, Buckle and 
Whewell, that isolated examples which lead standard practice 
by a half century or more, are to be observed during the 
growth of every art. Recognized standard practice is al- 
ways as conservative as it is permitted to be by trade com- 
petition, and usually changes very slowly. Principles may 
be discovered and understood, and a correct theory of de- 
sign and of practice may be made generally familiar, and 
often is, in a brief period; but the growth of application 



STEAM ENGINES FOR 



and the familiarizing of constructors and operatives with 
new mechanisms, and new methods of management, re- 
quires time, and is slow at best. Thus it has happened, 
that although the principles of steam engine economy were, 
in the main, well understood by James Watt, and some of 
his competitors, nearly a century ago, and have become 
well settled in later years, we are still far from a completely 
satisfactory solution of the problem, which, as stated by 
the writer elsewhere, may be enunciated thus: — * To con- 
struct a machine which shall, in the most perfect manner 
possible, convert the energy of heat into mechanical 
power, the heat being derived from the combustion of 
fuel, and steam being the receiver and conveyer of that 
heat." 



ELECTRIC LIGHTING PLANTS. 



II. 

Principles of Economy; Special Requirements. 

'' I ^HE principles of economical working, noted by James 
-*- Watt, and plainly stated by him, were but slowly 
recognized by others, and the improvement of the steam 
engine was, for many years, correspondingly slow. The 
principles that must govern the engineer, in the attempt to 
secure highest efficiency, may be summarized thus: 

1. The greatest practicable range of commercially 
economical expansive working of steam must be adopted; 
the fluid must enter the cylinder at the highest admissible 
pressure, and must be expanded down to the minimum 
economical pressure at exhaust. 

2. The wastes of heat must be made the least possible; 
all loss of heat by conduction and radiation from the engine 
must be prevented, if possible, and the usually much more 
serious waste which occurs within the engine, by transfer 
of heat from the steam side to the exhaust, by "cylinder 
condensation" and re-evaporation, without doing its pro- 
portion of work, must be checked as completely as is 
practicable. This latter condition, as well as commercial 
considerations, limits the degree of expansion allowable. 
It also dictates high speed of engine. 

3. The largest amount of work must be done by the 
engine that it can perform, with due regard to the preced- 
ing conditions. This condition compels us to drive the 
engine up to the highest safe speed, and to adopt the high- 
est practicable mean steam pressure. 



STEAM ENGINES FOR 



The first two of the above requirements give maximum 
efficiency of fluid, consistent with commercial economy, and 
the latter gives highest efficiency of machine. In addition 
to these requisites, which are not peculiar to any style of 
engine, or to any one of the innumerable applications of 
steam power, the adaptation of the machine to driving the 
dynamo-electric apparatus of an electric lighting plant, 
compels the designing and constructing engineer to meet 
certain demands which, although not peculiar to this work, 
are, nevertheless, more imperative here than elsewhere. The 
principal of these requirements are effective regulation, 
compactness, simplicity of parts, strength and durability, 
and small cost, both of original purchase and of repairs. 
In the attempt to meet these demands, the modern "high 
speed engine " has gradually taken shape. 

In the time of Watt, a pressure of seven pounds of 
steam, with condensation, and a low piston speed, equal, 
usually, in feet per minute, to about one hundred and 
twenty-eight times the cube root of the length of stroke, 
according to Watt's own rule, represented standard practice. 
As time went on, steam pressures and piston speeds gradu- 
ally rose, and when, in 1849, Corliss brought out the typical 
modern '''' Drop Cut-off Engine,'' pressures of sixty pounds, 
and speeds of piston reaching 450 feet per minute were 
becoming usual. At such speeds, the "drop cut-oif" was 
thoroughly effective, and the steam valve, detached from 
the driving mechanism, fell into its seat with sufficient 
promptness and accuracy, as to time of closing, to do good 
work; the governor had no other work to do than to detach 
the valve, and was thus able to regulate with an exactness 



ELECTRIC LIGHTING PLANTS. 



that is still beyond competition. These engines are very 
extensively used to drive the smaller electric light machines, 
and particularly where a considerable number are to be 
■driven together; they are not adapted to the work of driv- 
ing the large "dynamo," where it is desired to couple 
direct from crank-shaft to armature. 

As piston speeds increased, the drop cut-off became less 
satisfactory, where the load was variable. It became slowly 
understood, among builders and users of engines, that one 
important element of economy of fuel and cheapness in 
cost of engine is the maximum speed of engine consistent 
with endurance and safety. Speeds were, after a time, 
rapidly increased, the Porter-Allen engine leading in this 
movement, and small engines, working at high speed, dis- 
placed large engines of the older type. It soon became 
evident that this change must lead to the re-introduction 
of the " positive motion " classes of valve gear and expan- 
sion gear that Sickles, Corliss and Green had temporarily 
displaced, notwithstanding the fact that these builders had 
greatly increased the speeds of their engines. All the so- 
called " high-speed engines," which are best known in the 
market, are of this later type. The slower running engines 
are nearly all fitted with governors of the fly-ball class, 
geared, or belted, to revolve at a much higher speed than 
the engine itself ; but the great velocity of rotation of the 
new engines, from 200 to 500 revolutions per minute, in 
the small sizes, and often a piston speed of about 800 
times the cube root of stroke, permits the attachment of the 
governor directly to the shaft; and this is done in the later 
styles. This change of position of the governor, in turn, 



STEAM ENGINES FOR 



has led to a change in its construction. The balls, instead 
of being hung from a vertical revolving spindle by arms 
pivoted on that spindle, are attached to arms carried on the 
main shaft, or the driving pulley, and revolve in a vertical 
plane at right angles to the shaft; they are held in place 
against the action of centrifugal force by springs, and 
arranged to adjust the eccentric, and to vary the expansion, 
in a manner which will be plainly seen when studying their 
construction in the later sections of this paper, in 
which these engines will be described with the aid of care- 
fully made engravings. The high speed engine, as adapted 
to the work of directly driving the ''dynamo," therefore, 
may be described as a high pressure, non-condensing 
engine, of short stroke, and high speed of rotation, with a 
positive-motion valve-gear, and regulated by a governor, 
which is usually mounted on the shaft, and so attached as 
to alter the expansion by varying the lead of the valve. 
Its essential features are high speed of rotation, good regu- 
lation by a positive gear, economy, simplicity, and compact- 
ness. It is this engine only, which is found to do good 
work under these peculiarly exacting conditions. 

It is proposed to study the best known engines of this 
and the earlier classes, and to compare them, with a view 
to bringing out their peculiarities and their special merits, 
while the purchaser will, besides, study the machine which he 
proposes to buy, to determine whether its material and work- 
manship are as excellent as are the principles of its design. 

The conditions demanded can here be merely outlined, in 
the following resume' of the requisites of successful practice: 

1. Report on Machinery and Manufactures. R. H. Thurston. Vol. iii. 
Reports of the Scientific Commissioners of the United States to Vienna; 1873. 



ELECTRIC LIGHTING PLANTS. 13 

1. A good design, by which is meant: 

a. Correct proportions, both in general dimensions 
and arrangements of parts, and proper forms and 
sizes of details to withstand safely the forces which 

■ may be expected to come upon them. 

b. A general plan which embodies the recognized 
practice of good engineering. 

c. Adaptation to the specific work to be performed, 
in size and in efficiency. It sometimes happens that 
good practice dictates the use of a comparatively 
un-economical design. 

2. Good construction, by which is meant: 

a. The use of good material. 

b. Accurate workmanship. 

c. Skillful fitting and a proper " assemblage " of 
parts. 

3. Proper connection with its work, that it may do that 
work under the conditions assumed in its design. 

4. Skillful management. 

In the endeavor to secure these requisites, it is generally 
advisable to use steam at a pressure not far from one hun- 
dred pounds per square inch. The benefits of increasing 
pressure diminish so rapidly above this point, that it is not 
yet certain whether it will, with the simple engine, pay to 
carry pressure much higher. The ratio of expansion is to 
be determined with reference to this pressure, as well as to 
size of engine. It will usually be found even more wasteful 
to cut-off too short than to " follow " too far; and Rankine's 
principle of adjusting this point by consideration of the rel- 
ative cost of large and small engines, as well as the princi- 



14 STEAM ENGINES FOR 

pies controlling the economy of fuel, dictate, that for these 
engines, which are nearly always non-condensing and un- 
jacketed, the ratio of expansion must usually be low — say 
from three to five, as higher pressures range from sixty to 
one hundred pounds per square inch' — and that the termin- 
al pressure shall usually be kept some five or six pounds 
above that of the atmosphere. 

Moderate " superheating " is found advantageous ; but 
it is seldom carried beyond about a hundred degrees above 
the normal temperature of the steam. " Steam jacketing," 
as practiced in nearly all compound engines, is of advant- 
age; but is not usually considered to pay for the added cost 
and risk in engines of the class here considered, and espe- 
cially in high-speed engines. The " compound " engine has 
now found a place in this field. Smeaton's idea — or rather 
Watt's, first attempted on a large scale by Smeaton — of sur- 
rounding the working fluid with non-conducting surfaces, 
is not yet found practicable with the high steam pressures 
and temperatures now usual. Its final adoption, however, 
is beyond doubt, as it is a far more promising system of 
economizing heat, now wasted, than either superheating or 
steam jacketing. The latter, indeed, is a method of intro- 
ducing a waste to check greater loss. 

Careful protection of external heated surfaces of the 
cylinder against losses by conduction or radiation, is always 
practiced where it can be conveniently done, and parts 
which cannot well be so covered are highly polished. A 
well polished surface transmits very little heat. 

Back pressure, a frequent cause of waste of power, is 

2. Manual of the Steam Engine, Vol. I. § 25. 



ELECTRIC LIGHTING PLANTS. 15 

reduced by making the exhaust parts large, and the exhaust 
opening of the valve rapid, and by giving "lead" to 
the exhaust, so that the steam shall leave the cylinder just 
before, rather than just after, the return stroke begins. 

Friction is reduced to a minimum by carefully propor- 
tioning the journals, and by securing free and continuous 
lubrication with a good oil or grease. 

An engine in which all the above requirements are fully 
met is certain to be a good machine. 

It is not proposed to compare the steam engine with the 
gas engine, or with other motors. The gas engine is, in 
many cases, likely to prove useful in. consequence of its 
compactness, cheapness of first cost, freedom from rislc, and 
small expense for attendance ; but it is expensive in use of 
fuel, and is rarely as little liable to annoying interruptions 
of operation as the steam engine, and also possesses other 
minor disadvantages. Nevertheless, Otto and Clerk, and 
other inventors and constructors, have greatly improved this 
machine of late, and have brought the expenditure, in ten- 
horse engines, down to twenty cubic feet of gas, or less, per 
hour and per horse-power ; and although this is still double 
the theoretical figure, no one can say how soon the latter 
consumption may not be much more closely approximated 
to. The gas engine is certain to find work in this direction. 
Hot air engines, as yet, give less promise ; but it would be 
rash to predict their total exclusion from the field. 

Water-wheels, especially when used exclusively for sup- 
plying power to the lighting plant, are, where available, 
thoroughly satisfactory prime movers. 

In studying the steam engine from the standpoint here 



i6 STEAM ENGINES FOR 

taken, we will divide them, first, with reference to their 
method of driving the dynamo-electric machine, into two 
classes : 

1. Engines which may be used in driving by belt, and 
ivhich are not adapted for direct connection. 

2. Engines especially designed and constructed to be 
coupled directly to the " dynamo." 

The first class of engines is in very extensive use, and 
is, by many of the more conservative engineers, still pre- 
ferred to the second. The latter constitute the so-called 
"modern" type of engine, and are gradually coming into 
use, some engineers adopting them, both for direct and for 
indirect connection. The best engineers are not yet fully 
in accord in regard to the question, whether they have 
passed the experimental stage. 

The great changes marking the approach of the 
twentieth century are the general introduction of the 
multiple-cylinder engines having two or three and even 
four cylinders " in series," and the direct connection of 
the driving-engine with the driven electrical generator ; 
both having a common shaft, or shafts directly coupled, in 
such manner that both machines shall be employed at the 
same speed of rotation and all belting or gearing connec- 
tions then eliminated, giving thus a gain in simplicity and 
with great economy of floor-space. 



ELECTRIC LIGHTING PLANTS. 17 

III. 

Engines Indirectly Connected, only. 



THE CORLISS ENGINE. 

T~\IVIDING engines used in driving dynamo-electric 
-*— ^ machines into two principal classes — engines driving 
indirectly through gearing or belting, and engines directly 
connected to the armatures — we may profitably devote con- 
siderable space to the first class. And, although machines 
of the kind which have come to be distinguished by the 
appellation "high-speed engines" may be, and often are, 
indirectly connected, it is proposed to leave the examina- 
tion of such engines to a later article on directly connected 
engines, and here to describe only the " drop-cut-off " 
engines, or those with "detachable valve-gear," which can 
only drive the armature of the " dynamo " indirectly. 

The first drop cut-off introduced, had a form patented by 
Fred. E. Sickles, in 1841. This engine was first built for 
mill purposes, by Thurston, Gardner & Co., at Providence, 
R. I., that firm then holding the Sickles' patents, except that 
the marine engine business was retained by Sickles. The 
modern stationary engine was thus introduced, and was 
soon extensively made known among steam users by its 
superior performance when competing with the older engines, 
which were then usually arranged to expand steam about 
one and a half times by the lap of the single three-ported 
valve. A few engines were built of a better design, fitted 
with an independent cut-off valve on the back of the main 



STEAM ENGINES FOR 



valve. These two last named engines would, at best, with 
good boilers use five or six pounds of coal per hour, and 
per horse-power, where the Sickles valve-gear would bring 
the consumption down to four. 

Regulation was always effected by a governor controlling 
a throttle valve. This governor was usually a common fly- 
ball governor, and its deficiency in power and lack of 
isochronism, the distance of the regulating valve from the 
engine valves, and the range of motion required in its 
operation, and the resistance offered by the packing of the 
steam, altogether, made this combination a very ineffective 
regulating apparatus. Thurston, Gardner & Co., sub- 
stituted for this the Pitcher hydraulic regulator and a 
register valve, which gave a much better regulation; this 
contrivance was also isochronous, /. <?., it was capable of 
holding the engine at speed, whatever the variation of 
steam-pressure or of load. 

But an immense step in advance of this, then, best prac- 
tice was made by Geo. H. Corliss, a young Providence me- 
chanic, who had exchanged the role of sewing-machine inven- 
tor for that of the inventor of the most famous steam engine 
that has appeared since the time of Watt. The Corliss engine 
was patented in 1849, and rapidly came into use, its re- 
markable economy, when competing with the best existing 
engines, the peculiar business tactics of its builder, and the 
rapidly increasing demand for efficient, and especially well 
regulated, engines, combining to give it a wonderfully rapid 
introduction. 

The engine is an interesting illustration of a machine 
which is the representative of a peculiar type, each detail 



ELECTRIC LIGHTING PLANTS. 21 

of which is especially adapted to its place in that machine, 
and is characteristically different from the parts which per- 
form the same office in other engines. The leading features 
of this machine are: 

1. The use of four valves — two steam, and two exhaust 
— so placed as to reduce "clearance " to a minimum. 

2. The use of a rotating valve, capable of being cheaply 
and readily fitted up, of being easily moved, and of being 
conveniently worked by connections outside the steam 
spaces. 

3. The use of a " wrist-plate," caused to oscillate by a 
single eccentric, and directly so connected with all four 
valves that each may be given a rapid opening and closing 
movement, and be held open and nearly still, at either end of 
its range, by swinging the line of connection nearly into the 
line between centres, thus permitting nearly a full opening 
of port to be maintained during an appreciable interval, 
and a free and complete steam supply and exhaust. 

4. A beautifully simple and effective method of detach- 
ing the steam valve from the driving mechanism, and of 
insuring its rapid and certain closure at the proper moment, 
to produce any desired expansion of steam. 

5. A direct connection of the governor, so as to deter- 
mine the ratio of expansion, while so adjusting the power of 
the engine to the work to be done, that the variation of 
speed with changing loads becomes a minimum. 

6. Making this latter adjustment in such a way as to 
throw the least possible work on the regulating mechanism, 
and thus to give the governor the greatest possible sensitive- 
ness and accuracy of action. 



STEAM ENGINES FOR 



7. A form of frame and general design of engine, which 
gives maximum strength and stiffness, with least cost and 
weight. 

All these features are combined to form a steam engine 
essentially different, in general and in detail, from the 
engines contemporary with or succeeding it, except where 
the latter may properly be classed as Corliss engines. It 
rarely happens that an inventor succeeds in originating a 
plan so wholly and so essentially novel; and it is still less 
frequently the fact, that a peculiarly original device is 
found superior to all competing machines. In operation, 
the engine was found to exhibit a remarkable economy of 
fuel, and a singularly perfect regulation, and to be far more 
durable and more economical in cost of repairs, on the 
average, than rival builders supposed possible. It very 
soon took the leading place in the market. 

The inventor established himself at Providence, and put 
in operation a method of marketing his machine which 
was as novel and as successful as the mechanical device 
itself. He offered to put his engine in place of rival 
engines, either with a guarantee of a certain saving, and at 
a stipulated price, or, often, to take as his compensation 
the actual saving shown on the books in a stated time. 
This system was eminently satisfactory to the purchaser, 
both as making him safe against loss, and as giving him 
some of that confidence in the engine which the maker 
himself unquestionably possessed. Corliss' work fully 
justified his claims, and the expenditure of fuel was brought 
down to between three and four pounds per hour, and per 
horse-power, according to size and situation of the engine, 



ELECTRIC LIGHTING PLANTS. 23 

with occasionally much better figures in condensing engines. 

This engine is now built, not only by the Corliss 
Steam Engine Co., under the eye of the inventor, but by 
many other builders. It has found its way into every part 
of the world ; and the engineer visiting Europe will find a 
pleasure in observing the general adoption of this American 
invention in every country, and for every purpose. Euro- 
pean makers frequently modify the design, but rarely with 
the desired effect of securing an improvement in cost or 
efficiency, and very often with a decidedly contrary 
result. 

Corliss engines are now very frequently adopted in 
electric lighting, and are always belted to the dynamos. 
Their excellent regulation is as important a feature in this 
application, as is their economy in use of steam. When 
carelessly constructed, they are, of course, likely to prove 
wasteful and irregular in action. But that these engines 
can be made to give very perfect uniformity of rotation 
will be evident, when it is stated that the writer, in testing 
engines of this class, has found that the variation of speed 
was so slight as to be practically inappreciable, even when 
the amount of work thrown on or off, was a very large pro- 
portion of that done by the engine when working at its rated 
power. 

One other reason for the success of this engine is un- 
questionably the comparatively small cost of its construc- 
tion, where competing with the earlier forms of engine with 
detachable valve-gear. Its valve-faces, particularly, and 
their seats, are surfaces of revolution, and they, as well as a 
large part of the finished work about the engine, being 



24 STEAM ENGINES FOR 

almost wholly lathe-work, the cost of fitting up is com- 
paratively small. 

In detail, the engine consists, as shown in the illustration, 
page 19, of one of its standard forms, of a steam-cylindei 
sustained by any substantial connection with the foundation. 
The main pillar-block sustains the crank-shaft at the 
opposite end of the machine, and a strong brace, connecting 
these two pieces, forms, at the same time, a support for the 
crosshead guides. 

The four valves are placed at top and bottom of each 
end of the cylinder, their rotating stems projecting, and are 
moved by the "wrist-plate," set usually, as here, at the 
middle of the cylinder, the valve connections radiating to 
the four corners, where each is attached to the valve rock- 
ing-arm, the exhaust by pin-connections, the steam by a 
catch, which can be readily " tripped " by the adjustment 
of a little cam set on the valve-stem, behind the arm. 
When tripped, the steam valves are closed by a spring, or 
in engines now built by Mr. Corliss, by a "vacuum-pot," 
and by weights in his earlier engines, and in those of other 
builders. 

The governor is belted from a pulley on the main-shaft, 
and its oscillations are controlled by a "dash-pot," seen 
attached to the side of its standard. The governor, having 
no work to do but to set the tripping-cam, or the equivalent 
for it adopted by Corliss and others in various designs, is 
entirely free to adjust itself to the normal position due the 
speed of the engine, and thus is made perfectly capable of 
doing the best possible work Many foreign builders have 
attached the Porter loaded governor to this engine. The 



ELECTRIC LIGHTING PLANTS. 25 

advantage is less obvious here than in engines in which 
more strength of action is needed. 

From what has been stated, it is seen that the Corliss 
engine came into use in consequence of its combination, to 
an extent up to that time unequalled, of several special 
features. Some of these points are not necessarily peculiar 
to the Corliss type of engine; but they, nevertheless, were 
peculiar to that engine at the time of its introduction. 
The main points were : the rapid and wide opening of the 
steam and exhaust openings; the shortness and directness 
of the ports; the resulting small clearance and "dead" 
spaces ; the quickness of closure of the steam valves ; 
the adaptation of the main valve to the functions of 
a cut-off valve ; the connection of the governor to the 
cut-off gear in such a manner as to determine the point of 
cut-off without being itself hampered by the connection ; 
the location of the exhaust ports at the under side of the 
cylinder so as to drain the cylinder thoroughly ; and the 
simple, easily constructed form of the machine and of its 
details. 

The general form of the engine has been preserved 
by nearly all builders, and the parts of the valve gear 
and details of regulating mechanism have been seldom 
much modified. A few builders have, however, made 
changes which are worthy of notice, but which we have 
not time or space to study as they deserve. 

The action of the Corliss engine is as follows •} 

The valves are driven by the eccentric rod through the 
" wrist-plate," E^ vibrating on a pin projecting from the 

I. Manual of the Steam Engine, Vol. I. § 34. 



25 



STEAM ENGINES FOR 



cylinder. Links, E D, E D, E F, E F, take motion, from 
properly set pins on this wrist-plate, to the steam valve 
rock-shafts, D, D, and to the exhaust valves, E, E, moving 
them with a peculiar varying motion in such a manner as to 
open and close the ports rapidly, and to hold them open, when 
the valves are off the ports, in such a way as to give the 
least possible loss of pressure during the exit or the entrance 
of steam. The links leading to the steam valves are fitted 




The Corliss Engine. 



with catches, or latches, which may be disengaged, as the 
valve opens, at any desired point within about half stroke; 
and the time of this disengagement is determined by the 
rotation of a cam seen on the valve stem above D, which 
cam is rotated by the governor through the rod II, leading 
off to the left. The slowing of the engine, in consequence 
of reduced steam pressure or of increased load, causes the 
catch to hold its contact longer and the steam to follow 



ELECTRIC LIGHTING PLANTS. 



27 



farther, and the reverse. When the catch is disengaged, 
the valve is closed by a spring or weight attached to the 




vertical rods seen connected to the rock-shaft arm. Corliss 
uses a device in place of this which is not here shown. The 



28 



STEAM ENGINES FOR 



dash-pots are under the floor, in the case here illustrated, 
or on the column supporting the governor in the engines 
just referred to. It is always an air dash-pot. The device 
invented by Sickles was a water dash-pot. 






^ 




The standard form of Corliss valve is very well exhibited 
by the illustrations here given, which are taken from the 
drawings of Mr. Harris. 



ELECTRIC LIGHTING PLANTS. 



29 



Those marked A are the steam, and those marked B are 
the exhaust valves. Both consist, as is seen, of cylinders, 
parts of which have been cut away, leaving the working and 
bearing surfaces of no greater extent than is necessary to 
subserve the purposes of the valve. These surfaces are of 
the simplest possible form and are easily fitted up in the 
lathe. In order that they may come to a bearing with cer- 
tainty, and without regard to the position of the spindle 
relatively to the valve, they are made with a longitudinal 
slit into which fits, without jamming, the blade of the rock- 
shaft. The valves are thus allowed to come to a bearing, 
and even to wear down in their seats without causing leakage. 
The next Fig. shows the arrangement of this valve as 
seen in longitudinal section of the chest. As this maker 



FT cv 




Harris-Corliss Valve. 

constructs it, the stem goes through a fitted opening, with- 
out stuffing box, and the slight drip is carried off from 
the closed space at D ; thus none escapes into the 
engine room. The steel collar at F, which is shrunk on 
the stem, fits into the recess at <^ and serves as a packing. 
As the tendency of the stem to shift outward always causes 



30 



STEAM ENGINES FOR 



the collar to wear to a fit, it is not likely often to wear leaky. 
Another detail of interest in the Corliss engine is the 





"dash-pot." When the valve is suddenly closed, some 
device is necessary to prevent jar at the instant of its com- 



ELECTRIC LIGHTING PLANTS. 31 

ing to rest. This device is the dash-pot. The form adopted 
by Corliss consists of a shallow cup into which a piston on 
the valve stem fits, cushioning the enclosed air, and thus 
checking the motion of the valve without shock. This dash- 
pot, made by Watts, Campbell & Co., who have successfully 
introduced Corliss engines into electric light establishments 
in New York city and elsewhere, is that seen in the Figs. 

The annular piston, E, E, fits the cylinder, D, D, E, E, 
and a space, seen above B, forms a vacuum chamber which 
assists the spring or weight, closing the valve by the form- 
ation of a more or less complete vacuum, as the pis- 
ton is raised while the valve is opening. A small cock, 
not seen, is arranged to adjust the degree of ex- 
haustion of this chamber. When the valve has nearly 
reached its seat, the piston D, passes the opening from F 
into the outer space and the enclosed air then acts as a 
cushion, checking the movement of the valve. In the 
engines of these builders, great care is taken to keep the 
cold exhaust steam clear from the cylinder as it passes out, 
in order to prevent the condensation which occurs where 
this precaution is neglected. 

Many Corliss engines are already at work driving elec- 
tric lighting apparatus, and are giving good satisfaction, 
according to the testimony given the writer by the officers 
of the companies using them. One, built by the Corliss 
Steam Engine Co., is at work at Providence, R. I., driving 
many dynamos, and a number are in use in New York city, 
and other large cities of the United States and of Europe. 

At how high a speed they can be operated with satisfac- 
tion to the user is not definitely known. The writer has 



32 STEAM ENGINES FOR 



known one of these engines, coupled to a fast running roll- 
train, to be driven without apparent difficulty for several 
years at a speed of i6o revolutions per minute, although ot 
four feet stroke. This engine is still running. Those who 
use, as well as the engineers who build, this class of engines, 
however, are apt to be conservative and to prefer the mod- 
erate speeds with indefinite endurance, to higher speeds with 
a shorter life of engine and greater cost in keeping in 
repair; and to consider that the satisfaction of having a 
prime motor, which is not likely during their business lives 
to give them any trouble, is more than a corupensation for 
any possible saving in dollars and cents to be effected 
.by the adoption of the higher velocities of piston and of 
crank-shaft rotation. 



THE WHEELOCK ENGINE 

is an ingeniously arranged engine of the class considered 
in this division of the subject. 

Its form is seen in the accompanying engravings. 

The steam chest is placed below the cylinder and the 
steam and exhaust valves are set side by side, the latter 
serving both as induction and eduction valve, and having 
the same action, nearly, as the common three ported slide 
valve, while the function of the former is principally that of 
a cut-off valve. The latter, or main valve, is set nearest the 
end of the cylinder and the exhaust steam is thus permitted 
to escape directly and promptly from the engine. The 
valves are coned, slightly, and may be adjusted to take up 
wear, or to relieve pressure on their seats. These valves 



ELECTRIC LIGHTING PLANTS. 



35 



are carried on steel trunnions, and with hardened surfaces 
of contact are but little subject to wear. The steam or 
cut-off valve is set further away from the cylinder than in 
the standard arrangements of Corliss and other builders of 
that class of engines, and this enables the maker of this engine 
to secure a single port with reduced clearance and less 
liability to leakage, should the expansion valve leak. In 
this engine — and it should be the case in every engine in 
which the regulator is driven by belt — the connection from 
shaft to governor is so made that the breaking of the belt 
permits an automatic closing of the valve and the stopping 




The Wheelock Valves. 

of the engine. The regularity of motion of the class of 
engines described in this section, may be inferred from the 
fact stated in regard to the engine here studied, that it has 
been known to vary but a half revolution per minute when 
five-sixths of the load was thrown off. 

Engines of the class described in this section have dis- 
played an economy in the use of fuel that has been rarely 
excelled by the best type of compound engine, working 
under the same conditions of steam supply. With good 



36 STEAM ENGINES FOR 

boilers, they have given the horse-power with a consumption 
of two pounds an hour for condensing engines, and three 
pounds for non-condensing engines. They have quite 
often demanded but a ton of coal for 100 barrels of flour 
ground, in well arranged mills; and one and a quarter tons is 
a very usual figure. A number of good makers are now 
building such engines, and the purchaser can readily suit 
himself if desirous of selecting an engine of any grade, either 
as to cost or excellence of construction. They are well 
adapted to driving either large or small electric lighting 
plants; and, if purchased of a reliable maker, may be con- 
fidently expected to give satisfaction. 



THE GREENE ENGINE. 

"\ T EARLY all "drop cut-off engines" are constructed, 
■^ ^ like those described in the preceding article, 
with a single eccentric, which drives both the steam 
and the exhaust valves. Both sets of valves must, therefore, 
have the same motion relatively to the piston, except so far 
as their motion can be modified, as in the Corliss engine, by 
the method of connection of valve and eccentric. They 
must stop and start at the same instant, and their motion 
during their travel must be more or less similar. But such 
a system is controlled in its action by the necessary motion 
of the exhaust valve. That valve must be adjusted to 
open and to close very nearly at the beginning and 
the end of the return stroke, in order that the exhaust 
may be prompt and free, and that the compression shall 
be right. The movement of the gear, on the steam side, 




V.,^' 



ELECTRIC LIGHTING PLANTS. 39 

must thus be also one which shall open the valve 
to take steam at the commencement of the steam stroke, 
and, if the valve is not tripped, close the port at the end 
of that stroke. It is further evident, that if the valve is to 
be detached by its own motion, it can only be tripped dur- 
ing the forward part of its movement, and that, passing that 
stage, and commencing to return before the cut-off takes 
place, the valve must be allowed to remain undetached 
until the end of stroke, and steam must follow full stroke. 
An engine thus constructed, and so adjusted to its work as 
to cut-off at about half stroke, will evidently, if the work or 
the steam pressure becomes variable, be likely to operate 
very irregularly, at one time cutting off at a little inside 
half stroke, and then jumping to full stroke. This varia- 
tion of steam distribution may thus itself introduce a dis- 
turbing element, and the engine may give a very unsatisfac- 
tory performance. Such an adjustment of power of engine 
to the work to be done, does not often take place in engines 
of the class which is here studied, as the best point of cut- 
off is usually not far from one-third or one-fourth stroke, 
and the variation in the load is not often great enough to 
cause serious difficulty in the manner described above. 

One advantage possessed by the arrangement of valve 
gear, thus subject to criticism, is that, should, as sometimes 
happens, the valve fail to close, or should it lag behind 
very greatly, in fast running engines, it is certain that it 
cannot be left open beyond the end of that stroke, as the 
returning motion of the valve-gear will bring the latch into 
gear again, and will insure its closing. Mr. Corliss con- 
sidered this point of sufficient importance to make it inex- 



40 STEAM ENGINES FOR 

pedient to drive the steam valves by the method to be 
described in this article. It is undoubtedly an advantage 
to be able to secure such an arrangement of valve-gear 
that the ratio of expansion may be varied by the governor 
from the beginning to the very end of the stroke, so that 
the engine may adapt its steam supply to any load that 
may be thrown upon it, whatever the extent of that varia- 
tion may be, and to cut-off at any point from end to end 
of the stroke. This can be done by the adoption of a gear 
of the class known, for many years past, from the time of 
the earliest steam engines in fact, as the " plug-tree " form of 
valve-gear. It was this class of gear that was used on engines 
before the days of Watt, that greatest of inventors, for pump- 
ing out the deep mines of Great Britain — the Newcomen 
engine. It may be still seen in use on all so-called Cornish 
engines, which are to be found in the water works of this and 
other countries — the most costly, cumbersome, and unsatis- 
factory style of engine which has been applied to that kind of 
work in modern times. The distinguishing feature of this 
gear, is, that it is so adjusted, that the motion of the valve is 
produced by a mechanism which begins and ends its move- 
ment with the action of the piston; in the Cornish engine 
it is actuated by the engine beam. It is easy to obtain a 
motion of this character, by the use of an eccentric, by 
simply setting it so as to make its throw directly with, or 
opposite to, the crank. In such a case, it is seen that the 
exhaust valve must be driven by an independent eccentric, 
and the cost of the engine is thus somewhat increased. 
This is not a large item, however. The " Greene engine " 
is an engine fitted with such a valve-motion. 



ELECTRIC LIGHTING PLANTS. 



41 



In the accompanying illustration/ which exhibits this 
machine, the valves are seen to be four in number, as in the 
engines already described. They are flat valves, instead of 
cylindrical, and are thought by the inventor to be better 
than the latter, as being easier to refit when worn, and as 
being less liable to become leaky. The cut-off mechanism 
consists of a sliding bar, A, driven by an eccentric, set to 




Greene Valve Motion. 



give it motion parallel to the centre line of the cylinder, and 
with a movement co-incident, as to time, with the motion 
of the piston; of a pair of "tappets," C, C, set in this bar 

I. Manual of the Steam Enprine, Vol. I. p. 102. 



42 STEAM ENGINES FOR 

and adjustable vertically in such a manner as to engage the 
rock-shaft arms, B, B, on the ends of the rock-shafts, E, F, 
which rock-shafts are attached to the valve-links inside the 
steam chest; of a set of springs which hold these tappets 
up to their work, and in contact with the " gauge-bar " 
behind the bar, A, and out of sight in the drawing. This 
gauge-bar is adjusted to the proper height, and is varied in 
position, as the load varies, by the action of the governor 
which is connected to the gauge-bar by the rod extending 
up to it at G. The exhaust valves are seen below, and are 
driven by the second eccentric there shown. They are so 
placed as to thoroughly drain the cylinder of all water 
carried into it by priming, or produced by cylinder con- 
densation. The eccentric driving these valves is set 
at right angles to the position of the crank. In con- 
sequence of this independence of the two sets of valves, 
this engine can cut-off at any point in the stroke during a 
complete half revolution of the crank. This form of engine 
was invented by a Providence mechanic, Mr. Noble T. 
Greene, and was patented in the year 1855. Mr. Greene, 
then of the firm of Thurston, Greene & Co., introduced this 
engine a few years after the merits of the drop cut-off had 
been proven by Sickles and Corliss so fully that it was easy 
to secure a market for new devices of this class; and the 
introduction of this engine has had much to do with the 
rapid progress of these more economical kinds of engine. 

The form of the engine has been somewhat modified at 
various times, although its characteristic features have been 
carefully preserved. The steam valve, as designed by the 
writer, who, at the time of its first appearance, had an 



ELECTRIC LIGHTING PLANTS. 



43 




Thurston's Valve. 



occasional opportunity to exercise his powers as a designer 
on this engine, is seen in the next Fig.^ 

The valve, G, H, cover- 
ing the steam port, Z>, in the 
cylinder. A, B, is driven by 
the rod, /, /, which is con- 
nected to the rock-shaft, M, 
by the arm, L, K, in such a 
manner that the line, K, /, 
will, when prolonged, inter- 
sect the valve-face at its middle point Gj it is thus so set 
that the line of action of the link, K, I, meeting the valve 
seat directly under the middle of the valve, does not 
produce any tendency to rock the latter, and thus to cause 
wear at the edges, or leaks of steam past the valve into the 
port. 

The latest form of the Greene engine, familiar to the 
writer, is that now constructed by the Providence Steam;. 
Engine Co., and shown in the large illustration, page 35. In 
this engine, the steam valves are connected to the cut-off 
mechanism, by a set of rods or stems running parallel to 
their seats, and emerging into the air through stuffing 
boxes, properly provided with easily set and easy working 
packing; these valve stems are connected to the rock-shafts, 
and are driven as in the arrangement already described, 
very nearly; this design has some advantages over the old, 
in keeping the working parts, and especially the joints, out 
of the steam space. The exhaust valves are gridiron slides, 
set to travel across the line of the cylinder, and driven from 



1. Supplied by D. Appleton & Co. 



44 



STEAM ENGINES FOR 



a horizontal rock-shaft, extending forward to the eccentric 
on the crank-shaft; the governor is a Porter loaded 
governor, driven by a belt from the main shaft; the cut-off 
mechanism is illustrated in the last of this series of illustra< 
ticns. 




Greene Trip Motion. 



The tappets. A, A, are carried by the rock-shafts, y, 
J, which, in turn, drive the arms, F, -F, and the valves 
attached to the stems, G, G, passing through the stuffing 
boxes, H, Hj the tappets, B, £, engage these rock-levers, 
and are adjusted vertically by the governor rod, D, and 
held up against the gauge bar or the rock-lever, as the case 
may be, by the springs set in the sliding bar. When the 
speed of the engine is above that for which the engine is 
set, the governor, acting through the rod, JD, depresses the 
tappets, and they do not retain their connection with the 
rock-lever as long as when at normal speed; when the speed 



ELECTRIC LIGHTING PLANTS. 45 

falls below that fixed by the constructor, the governor rod 
rises, and the tappets are thus permitted to rise, and to 
remain in contact with the rock-lever, holding open the 
steam valve for a longer period than before. The longer the 
valve is to be kept open, and the farther the steam is to 
follow, therefore, the wider does the port open to steam. 
When the tappets travel to the point of cut-off, they swing 
clear of the rock-levers; the weights, acting together with 
the pressure of steam upon the valve-stem area, quickly 
shut the port, and the steam is allowed to expand from that 
point on to the end of stroke; the higher the tappets are 
permitted to rise, by the elevation of the gauge-plate, the 
greater the ratio of expansion; the further they are 
depressed, the shorter the cut-off. As these engines are 
constructed, they are capable of cutting off steam anywhere 
between the beginning and three-quarters stroke; the latter 
limit is determined by the lead, and by the margin thought 
necessary to secure certainty of closure of the valve, when 
tripped, before the piston reaches the end of its stroke. 
To follow farther would not be likely to be of advantage, as 
the gain in the mean total pressure would be compensated 
by the loss due to a retarded exhaust. A safety stop- 
motion is combined with the governor connection, in such 
a manner, that if the belt breaks, or is thrown off its pulleys, 
the steam will be at once shut off, and the danger of acci- 
dents, such as sometimes occur with a run-away-engine, is 
avoided.' The valves and seats on the exhaust side are 
both easily removable, from the outside, have outside con- 
nections, and are readily adjusted. 

T. A device now usual with detachable valves. 



46 STEAM ENGINES FOR 

These engines have been, next to those of Corliss, the 
pioneers in the movement, during the past generation, 
toward economical working of steam. A double engine 
upon this plan, substantially, by the firm of Thurston, 
Gardner & Co., nearly a quarter of a century ago, from 
designs prepared by Mr. E. D. Leavitt, Jr., for a well- 
known Eastern mill, had two jacketted cylinders, 26^ 
inches in diameter, 5 feet stroke of piston, made 50 revo- 
lutions per minute, with steam at 100 pounds pressure in 
the steam chest, and, on trial, worked down to a consump- 
tion of 1.98 pounds of coal per horse-power and per 
hour; the guarantee was 2 pounds. Its fiy-wheel, designed 
by the writer, who was then just out of college, weighed 
about 20 tons, was fitted up as a mortice gear, with cut 
hickory teeth, and was given extremely small side clear- 
ance; the motion of the engine was so smooth, however, 
that the presence of the gear was hardly noticeable. This 
engine was fitted with the gridiron slides, as in the above 
illustration; they were driven by sliding cams, thus ob- 
taining a rapid opening and closing of the exhaust, and a 
slow movement while in the intermediate position, with the 
port either open or closed. This was a remarkably good 
piece of work for that time, and has not often been 
excelled since. 

This engine, like other engines with drop cut-off valve- 
motion, is not adapted to such high velocity of rotation as 
to permit it to work safely at the speed of even the largest 
and slowest of the two-pole "dynamos; " but, belted to the 
machine, it will give as great economy, and as great per- 
fection of regulation, as engines of the preceding class. It 



ELECTRIC LIGHTING PLANTS. 47 

is evidently so arranged that no load is thrown upon the 
governor, and the effort to detach the steam valve is, there- 
fore, not liable to cause any oscillation in the cut-off gear, 
or variation in the speed of the engine. In all these en- 
gines, the difficulty met with by the designer is, not to 
secure this independence of the governor from the action 
of the valve-gear, but to prevent the irregularity which 
comes of the oscillations of the governor itself. The dash- 
pot attached to the governor, or, sometimes, a friction 
mechanism, prevents such irregularity. 

This valve-gear does no't as conveniently adapt itself to 
the vertical engine as some others, but one of the first 
engine-cylinders ever designed by the writer, was built with 
this gear, and was set vertically. It gave perfect satisfac- 
tion, if the fact that it was never reported to the shop for 
repairs, so far as the writer has yet heard, may be taken as 
evidence of its successful operation.^ 

This engine was introduced over a quarter of a century 
ago, in the face of a strong competition from the Corliss 
engine — a fact which is, perhaps, the best evidence that it 
had • merit — and by the same methods which Mr. Corliss 
had proved so effective. Guarantees were given of per- 
formance, and forfeitures were provided for in the contract; 
or else the agreement was accepted to take as payment the 
saving actually effected in a fixed period of time — usually 
from two to five years, according to the character of the 
machine displaced. One of these engines, with which the 
writer was familiarly acquainted through his indicator, and 

I. This engine is still (1895) in use, after 27 years' service, and drives a set of 
dynamos at South Webster, Mass. 



48 STEAM ENGINES FOR 

which displaced the rival engine on such a guarantee, has 
now been in operation 23 years, and is reported to be to- 
day still in perfect order. The engine referred to above as 
having given so excellent a performance, was put in under 
an agreement by which the builders agreed to forfeit $1,000 
per ^ pound that the coal consumption should fall short 
of the guarantee. The manufacture was interrupted for 
some years by an injunction secured by Mr. Corliss, after 
a suit brought by him for infringement, but was recom- 
menced after the expiration of the Corliss patent, and has 
proved a successful enterprise, notwithstanding the fact 
that its constructors have depended, apparently, upon the 
performance of the engine itself for advertisement — a con- 
servative system of doing business which few manufacturers 
adopt, at present. 

All three of the great inventors and introducers of the 
modern American type of steam engine — Sickles, who 
brought into use the drop cut-off ; Corliss, who gave the 
stationary engine its now standard form, as well as devised 
his peculiar valve gear; Greene, who applied the principles 
of this system of working steam to the plug-tree form of 
valve gear, — are now (1890) living. Mr. Corliss has 
acquired wealth, as well as fame ; his predecessor and his 
rival, however, have attained less fame — much less than 
they are entitled to, and ,still enjoy all the advantages 
which poets ascribe to the possession of small means.' 

1. Sickles and Corliss have since died, leaving behind them a legacy to the 
world, in their great inventions, the value of which cannot be estimated. Mr. 
Greene still lives (i8g6). 



ELECTRIC LIGHTING PLANTS. 51 

There are other engines belonging to the class here 
considered — the engines having a detachable cut-off valve 
closed independently of the motion of the valve-gear, — of 
which the space proposed for these articles will not permit 
description. Among these are the Wright engine, con- 
structed by one of the oldest and best known designers in 
the country; the Brown engine, a machine which has been 
extensively adopted for driving mills in New England, and 
is famous for the excellence of its workmanship and finish, 
as well as for its durability and efficiency; the Fitchburg 
engine, and others. 



52 STEAM ENGINES FOR 

IV. 
Engines Capable of Direct Connection. 



THE PORTER-ALLEN ENGINE. 

'' I ^HE essentials, in the construction of the steam engine 
-*- with a view to the economical production of power, 
as has been seen in the introductory part of this series of 
articles, include special provision against loss of heat and 
condensation of steam, at entrance into the steam cylinder, 
by the action of the metal surfaces to which it is exposed 
on all sides at the beginning of the stroke. One of the 
methods of securing this economy in the working of steam, 
has been stated to be the driving of the engine up to the 
highest safe velocity of piston, and giving it a maximum 
speed of rotation. The time allowed for condensation of 
each charge, and for the necessary change of temperature 
preceding such condensation, is thus reduced, and the 
amount of steam condensed being thus made a minimum, 
in any given time, the percentage of loss of the increased 
quantity of steam worked off by the engine becomes the 
least possible. The engine does a greater amount of work, 
and is subject to less loss. Thus the work to be done being 
fixed, it is done by a smaller, and, other things being equal, 
a less costly engine, and at the same by a more economical 
machine. 

Although this seems a sufficiently simple and axiomatic 
philosophy, and although the general tendency of practice 
in steam engineering had been plainly in this direction for 



ELECTRIC LIGHTING PLANTS. 55 

many years, these points had not, up to a comparatively 
recent time, been recognized by constructing engineers, and 
their progress had been slow and difficult. The older firms 
"vho were engaged in the building of what were then called 
" expansion engines," were the first to detect this movement 
and its cause, and they led off, in a very conservative way, 
toward the construction of faster engines. The firms 
already mentioned as leading in the movement toward cor- 
rect practice, came up to speeds far ahead of those common 
among other makers, and secured an advantage that was 
sufficient to prove unmistakably that they were in the right 
track. They did not, however, modify their designs in any 
great degree, with a view to adapting them to very high 
speeds. Their valve-gears were not of a kind well 
fitted to high speed of rotation; the builders, were them- 
selves disinclined to accept the risks undeniably attendant 
upon rapid change in this direction, and the public to whom 
they looked for a market were not educated up to such a 
point as would make it safe to attempt to go on very 
rapidly. A rather slow engine, with its comparative 
immunity from risk of serious accident in case any little 
derangement should occur, and with its greater durability 
under the ordinary conditions of use, was, by the great 
majority of designers, builders, and steam users, thought a 
far better investment than a fast engine, however well 
adapted to the radical illustration of a very interesting, but 
apparently impracticable, philosophy. 

The first man to take up this matter with a will, and 
with a faith and a determination that were equal to the 
task, was Mr. Charles T. Porter, a young lawyer turned 



56 STEAM ENGINES FOR 



engineer, and Mr. John F. Allen, when the writer first knew 
him, a skillful mechanic, who was showing the natural bent 
of a real inventor, in the production of new devices, while 
engaged in the management of some of the best engines of 
30 years ago. The valve-gear of the Porter-Allen engine 
is the invention of Mr. Allen, and its governor and general 
arrangement are due to Mr. Porter. It was Mr. Porter, 
also, who, by his courage, persistence, skill in business, and 
general good sense and management, finally, after years 
of struggle to secure good construction and workmanship, 
brought the engine into use in spite of every discourage- 
ment, whether due to circumstances, to direct opposition of 
competitors, or to public sentiment in favor of conservatism. 
There are some interesting problems which present them- 
selves to the engineer who attempts to design an engine to 
be operated at very high speed — problems which are by no 
means easy of solution, except to the boldest of innovators. 
One of these points of difficulty has already been considered. 
When the speed of revolution is increased, it is evident that 
a limit must sooner or later be attained at which the drop 
cut-off must be exchanged for some " positive motion " 
gear. But the various forms of such gearing familiar to 
engineers when Messrs. Porter and Allen became acquainted 
with each other, years ago, the still common three-ported 
valve, such as is used on locomotives, the Meyer valve with 
its cut-off valve on the back of the main valve, and kindred 
devices, were not adapted to the conditions sought by the 
engineer looking for a good system of expansion. They 
were simple and inexpensive, and could be used at any 
practicable speed of engine; but they did not always give a 



ELECTRIC LIGHTING PLANTS. 57 

satisfactory distribution of steam. They usually produced a 
retarded steam supply, a " throttling " of the steam at the 
point of cut-off, which was not at all such as would satisfy 
the engineer familiar with the prompt action, and the 
" sharp corners " of the indicator diagram from the class 
of engine then taking the market. The dependence of the 
several parts of the motion upon each other was another 
objection to these devices, and the load which they threw 
upon the governor was a fatal defect, as the governor was 
then arranged and connected. Mr. Allen's invention placed 
in the hands of Mr. Porter just the device that he needed 
to carry out his idea of a fast engine. 

This arrangement consists of a single eccentric driving a 
link motion to operate the steam valve and to work the 
exhaust at the same time. The link is controlled by a 
Porter governor, and is so connected and driven that the 
gear may be readily and quickly adjusted by the governor 
to any desired point of cut-off. 

The eccentric and link are shown in the next illustra- 
tion. The eccentric is set on the shaft in such a position, 
that its motion is co-incident with that of the crank. The 
link is a slotted curved arm, forming one piece with the 
eccentric strap, pivoted at the middle on trunnions sustained 
by an arm rocking about a pin set in the bed of the engine. 
The upper end of the link carries a pin, from which a rod 
leads off to the exhaust, which is driven without variable 
connections. The link-block is fitted to work in the slot 
of the link, from the end nearest the exhaust rod pin, down 
to the point opposite the pivotal point at which the trunnions 
are set. When it is at the upper end, the throw of the valve 



58 



STEAM ENGINES FOR 



is a maximum; when at the lower point, it is a minimum. 
A-s the link-block is moved up and down in the slot, the 
motion of the valve is varied, and the ratio of expansion 
correspondingly altered. By an ingenious adjustment of a 
still more ingenious form of valve-motion, it is thus possible 




The Allen Link. 



to obtain a valve movement of perfect precision at all 
speeds, and on both the forward and the backward stroke, 
with a quicker closing action, as the cut-off is later. The 
steam is. allowed to enter the cylinder, at nearly boiler 
pressure, almost up to the point of cut-off, and the expan- 
sion line is a smooth curve very nearly from the junction 
with the steam line. 



ELECTRIC LIGHTING PLANTS. 59 

This form of indicator diagram has been usually con- 
sidered peculiar to the class of engine described in the pre- 
ceding articles. In this case, the diagram is nearly as sharp 
in the corners as those from a drop cut-off engine. The 
range of expansion is from the beginning of the stroke to 
about five-eighths. 

There are four valves, as shown in the next Fig., which 
is a section through the steam cylinder showing valve, ports, 
and general construction. The two valves at the upper side 
of the cylinder are the steam valves; the lower are the 
exhaust valves. This section is, however, horizontal, the 
valves being set on their edges at either side of the cylinder. 
The exhaust valves are so placed as to drain the cylinder of 
any water that may have entered with the steam, or may 
have been produced by internal condensation. Both sets of 
valves are so made, and set, as to be well balanced, and 
so as to be capable of having the wear taken up when it 
occurs. All these valves are provided with pressure- 
plates, which are adjustable by hand, to make them steam 
tight, as well as to secure a perfect balance. Each valve 
is placed in a separate valve-chest, and can be independently 
adjusted. Each valve opens four ports; each is so set, that 
it is actuated by a rod in the line of its own centre; and all 
are thus rendered but little liable to either wear or leakage 

The rock-shaft arm on the intermediate rock-shaft, 
seen in the large Fig. between the eccentric and the 
steam valve stem, assists in securing the quick opening and 
closing motion essential to a satisfactory distribution of 
the steam. 

The features which have now been described, are not 



6o STEAM ENGINES FOR 

necessarily distinctive of a "high speed engine." A posi- 
tive motion valve-gear, and a good steam distribution, are 
desirable in such engines, and the first point is, in fast run- 
ning machines, an essential requisite; but the Allen engine, 
so far as it has been described, may be as well considered 
a slow as a fast engine. There are some details, to which 
"ve are now to turn our attention, which are essentially and 
peculiarly characteristic of the class to which this machine 
is assigned. Among these points are the strength and rig- 
idity of parts which distinguish such engines; the great 
nicety of fitting; the excellence of all material in every 
part exposed to the straining action of inertia, and the 
minor but yet important modifications of details to adapt 
them to service in a machine, in which the slightest play in 
joints or bearings will be certain to make trouble. The 
bed is of peculiar design and is enormously stiff and solid, 
especially in those parts which take the stresses of the re- 
ciprocating pieces. It is broad and deep, with the line of 
thrust of piston rod carried close to its surface between the 
guides, and with a box form which gives great resistance to 
forces tending to twist it. 

The steam cylinder is secured to the bed by the end, a 
construction adopted by Corliss many years ago, and one 
which gives all desirable strength, with freedom from those 
strains which come of connection of two large masses at 
different and constantly varying temperatures. The whole 
of its exposed surface is covered with lagging to prevent 
loss of heat by radiation. The main journal boxes are 
made in four pieces, and are set up by adjustable wedges, 
so set as to avoid the springing of the shaft that is some- 



Jip, Ft fi ^tn^ 




ELECTRIC LIGHTING PLANTS. 63 

times found to occur with a less effective arrangement. 
The main-shaft journals, and the journals of the crank-pins, 
are made with especial care, skillfully ground to size and 
form, and nicely finished before the engine is assembled. 
The pin is always of " mild " steel, carefully case-hardened 
to give it a surface that will wear well and will not " cut." 

The provisions for lubrication in such engines are not 
the least important of its details. The engine presents 
some neat devices in this respect which we have not space 
to describe. 

One of the most remarkable and interesting of the fea- 
tures, which especially adapt this engine to great speed of 
rotation, and one, the developement of which, in its theory, 
as well as in practice, is due to Mr. Porter, is a peculiar 
adjustment of weight of moving parts to the equalization of 
stresses on the line of journals between the piston and the 
crank-shaft. When the steam is allowed to follow the pis- 
ton only to some point early in the stroke, the ratio of 
expansion being made, as is usual, between three and five, 
the rapid fall of pressure, during expansion and up to the 
end of the stroke, causes a very great variation in the effort 
exerted upon the crank-pin and other journals. As the 
maximum pressure occurs when the crank is passing the 
centres, and while the work done usefully is, in consequence 
of the slight travel of the piston, very little, and as, at the 
same time, the considerable movement of the pin under this 
pressure causes a considerable loss of work by friction, and 
as it is advisable to secure a uniform effort producing rotation, 
it is evident that it is desirable to find a method, if possible, of 
equalizing the pressure throughout the stroke without sacri- 



64 



STEAM ENGINES FOR 



ficing the advantages of expanding the steam. The action 
of inertia in the moving parts is made by Mr. Porter the 
means of securing this result. 

At the beginning of the stroke, the inertia of the piston,, 
its rod, the crosshead, and to a certain extent the connect- 
ing rod, all reciprocating parts, causes them to offer a cer- 
tam resistance to the accelerated motion which they are 
compelled to take up. This resistance becomes less and 
less up to zero at half stroke, the point at which their velo- 
city is a maximum. Passing this point, they are rapidly 
retarded, and this same property of inertia causes them to 
offer a resistance to retardation, which resistance now is felt 
as an impelling force at the crank-pin. Thus, the effect of 
the presence of these heavy masses in the line of connec- 
tion, produces a reduction of pressure upon the pin at the 
commencement, and an increase of pressure at the end of 
stroke. But, in consequence of the varying action of the 
steam producing an excess of pressure at the beginning, 
and a deficiency of pressure at the end of stroke, we may 
combine these two effects, and the result is a comparatively 
uniform load upon the crank-pin throughout the stroke. 

This compensation is capable of being, in many cases, 
very nicely adjusted by properly proportioning the weight 
of the reciprocating parts. As engines are usually propor- 
tioned with a view to strength of parts simply, the piston, 
crossheads, and rods are too light to be of much service in 
this way. Mr. Porter adopted the plan of making his pis- 
ton and crosshead of such weight that the equalization of 
pressures should be the most complete possible, and this 
involved making them decidedly heavier than they are made 



ELECTRIC LIGHTING PLANTS. 65 

in common practice, even when his engines were driven up 
to a G,peed which had never been before attempted in sta- 
tionary engine practice. It is evident, however, that at some 
■ higher speed, the weights of these parts, as proportioned 
for strength simply, would be sufficient to give this desir- 
able adjustment of the load on the crank-pin. There is no 
reason to suppose that this, which the writer has called 
natural speed of the steam engine, may not be at some 
future time attained. 

An interesting fact in this connection, is that Mr. Porter, 
although not professionally a mathematician, or educated 
as an engineer, first worked out the relations of these forces 
by a simple process, and applied his results to his practice, 
and that, subsequently, at his request, a distinguished ma- 
thematician. Dr. Barnard, President of Columbia College, 
attacked the problem by the methods of the higher analysis, 
and revealed the laws involved, and verified completely the 
work of the engineer. (See Man. St. Engine, Vol. II. § 116.) 

The Compound Condensing Porter- Allen Engine, having 
cylinders 24 inches and 46 inches diameter, by 42" stroke of 
pistons, makes 120 revolutions per minute, at which speed 
it is rated at about i,ioo-horse-po\ver capacity. 

On the main shaft is carried the armature of an 800- 
kilowatt dynamo. The same general arrangement is fol- 
lowed in all sizes where this type of engine is connected 
directly to an electric generator. An advantage of the 
higher speeds, where direct driving is adopted, is the reduced 
first cost of the dynamo. The Porter-Allen engine is built 
to run at various speeds, from 360 revolutions per minute 
for 100 horse-power to 120 revolutions per minute for 
1,500 horse-power. 



66 STEAM ENGINES FOR 

Engines of this class have many advantages, consequent 
upon their high speed; they are, other things being equal, 
more economical in the use of steam; they can be given a 
very much smaller fly-wheel; they have, in consequence of 
the enormously reduced weight of wheel, less friction; they 
are more easily held to their speed by the governor; they 
are less subject to variation of speed between beginning and 
end of any one stroke; and they are usually less trouble- 
some and expensive to connect to the load than slow run- 
ning engines. These advantages are common to all classes 
of engines, as they are driven up to high speeds; the class 
here considered is simply better fitted to realize these 
advantages than the older forms of engines, because they 
are especially designed for high speed. The objection to 
the "high speed engine," is the increased risk of wear, and 
of accident due to their rapid motion, and especially the 
risk, that when accidents do occur, as they will now and 
then in the best regulated establishments, they may be 
vastly more serious than with engines working at ordinary 
speeds. The object of the precautions which are taken by 
builders of fast engines, are all directed to meeting this 
contingency, and to making their machines safe against 
accident. These precautions are seen to be the strengthen- 
ing, and especially the stiffening, of all the parts exposed to 
the stresses due to the action of inertia in the reciprocating 
pieces; the adjustment of all parts to each other in such a 
manner as to avoid spring; the use of the best material; 
an effective system of lubrication; and the securing of the 
most perfect workmanship. 

Watt once congratulated himself that he was able to get 



•'■iTlii,, 




m 



'I'. w_ 



ELECTRIC LIGHTING PLANTS. 69 

a steam cylinder that only lacked three-eighths of an inch 
of being truly cylindrical; the builder of the "high speed 
engine " of to-day works to the thousandth of an inch, in 
longitudinal measurements, and gets his cylindrical journals 
exact to the twenty thousandth, perhaps to the fifty thou- 
sandth of an inch, a quantity which can be detected by a 
good workman. The contrast illustrates well the progress 
of a century in accuracy of workmanship where nicety is 
required. Such nicety, only, can make a fast running en- 
gine safe; such accuracy does make it safe, and such 
engines now do their work uninterruptedly, year in and year 
out, and are found to require no more than that ordinary 
care which all engines are expected to receive. 

A Porter-Allen engine, from the " Southwark Foundry," 
supplied power to the Weston, Edison, and the Thomson- 
Houston Electric Light Companies at the Railway Exhibi- 
tion at Chicago, May and June, 1883. 



THE buckeye" engine. 

THE engine last described was a long time alone in the 
field as a "high-speed engine." The principle rep- 
resented by its designers was recognized as correct by every 
intelligent engineer, and it was admitted that the fast engine, 
other things being equal, would prove the most economical 
in its expenditure of heat, as well as in its efficiency as a 
machine subject to friction. But builders were not able to 
bring themselves to accept what seemed to them the risks 
incident to high speeds. The pioneer in this new field was 
not altogether successful for a time, and it seemed to be 



70 STEAM ENGINES FOR 

certain at one time, that the engine, despite the pluck, the 
persistence, and the skill of its indefatigable promoter, must 
retire from the market. But no discouragement could quite 
destroy confidence in this engine, which had become the 
embodiment of the most recent phase of progress. Grad- 
ually, one difficulty after another was overcome; parts were 
strengthened and given satisfactory proportions; the mate- 
rials were improved and the workmanship of the machine 
was made as nearly perfect as the best tools, handled by the 
best workmen, could make it. A little gain was seen each 
year, and, after a time, it was seen that the new class of 
steam engine had " come to stay." 

One of the first engines to come into the field after this 
period of doubt had closed was built by an enterprising firm of 
Western manufacturers. This was the "Buckeye Engine," 
designed by Mr. J. W. Thompson, and built by the Buckeye 
Engine Co., at Salem, Ohio. The engine did not start as a 
radical competitor of the pioneer engine; but it was from 
the beginning, a moderately high-speed engine. It was 
fitted with a positive motion "automatic " valve-gear and a 
balanced valve, and had a stability and an excellence of 
workmanship that made it safe at fast speeds ; while the 
peculiarities of its construction were such as gave it a very 
high place as an economical machine. It was capable of 
meeting in competition the best engines of the day. 

The form given the larger sizes of this engine is seen 
in the preceding Fig. The general arrangement is not 
essentially different from that of the Corliss engine, which 
has been described in earlier articles. 

The cylinder is carried on a pedestal, as is the latter; 



ELECTRIC LIGHTING PLANTS. 7t 

the frame consists of a girder uniting the cylinder and the 
main pillow block and carrying the guides; the crank-shaft 
end is carried by another pillow block. The main frame 
is, however, supported by a strut which is now usually seen 
in other engines, and which takes the load tending to spring 
the girder under the guides. The construction of the cylin- 
der, and the arrangement of the valves, is shown in the 
next Fig. 

The live steam is taken into the steam-chest at A, passes 
through the passage, a, a, through the openings, D, D, into 
the box-shaped valve, B, B, and thence through the ports, 
b, b, into the cylinder, as the ports in the cylinder are alter- 
nately brought opposite those in the valve. The cut-off 
valve is formed of two sliding plates, C, c, connected by 
rods, C, and sliding on seats formed on the inner, or work- 
ing, side of the main valve, so as to cover the main steam 
ports alternately, and at times which are determinable by 
the governor. The stem, g, driving this valve, passes 
through the main valve stem, which is made hollow for that 
purpose. The cut shows the steam entering the cylinder 
at the left, and the cut-off valve just beginning to slide over 
the port, while the exhaust is taking place at the right, past 
the end of the main valve, through the chest, and around to 
the exhaust pipe seen partly dotted at F. At e, e, are seen 
two "relief chambers," which receive live steam from the 
steam valve through holes, f, f, and thus balance the valve 
at a time when the pressure on the seat caused by the then 
excessive area of the balance openings, D, d (which open- 
ings must be made sufficient in area to produce a slight 
pressure of the valve on its seat when the tendency to lift 



72 STEAM ENGINES FOR 

the valve from its seat is greatest), is overbalanced. These 
holes only fill when this relief is needed. The equilibrium 
rings, D, d, seal the joint between the valve and the dia- 
phragm separating the steam-chest, a, a, from the exhaust- 
chest J^. 

The governor is of a type that has not been seen in the 
engines previously described. It is shown in the following 
illustration, page 68. 

In the common " fly-ball governor," the two balls revolve 
about a vertical spindle, to which they are attached by a 
pair of arms in such a manner that they may take any posi- 
tion that the resultant action of gravity, centrifugal force, 
and the pull on the supporting arms may give them. A 
defect common to all governors of this class is that the 
force tending to pull the balls downward is perfectly uni- 
form. Gravity never changes at any one place. The posi- 
tion taken by the balls, at any fixed speed of engine, is 
always the same; the connection of the balls with the regu- 
lating mechanism, is one which always preserves a fixed rela- 
tion between the position of the governor balls and the posi- 
tion of the regulating apparatus. Thus it happens that the 
engine can never be kept precisely at speed, unless the speed 
is such as will give the governor exactly its normal position 
and, at the same time, such that the valves shall supply just 
the normal quantity of steam to the engine. With reduced 
steam pressure, the engine drops to a slightly lower speed, 
and runs at that speed instead of the proper number of 
revolutions; when the load decreases, the engine runs at a 
little higher speed than is intended; and no method of 
attaching that form of governor can give absolutely uni- 



ELECTRIC LIGHTING PLANTS. 



form speed. If, however, we can substitute for the action 
of gravity, a force which can be made to vary with change 
in the position of the balls, in such a way that the variation in 
the opening of the throttle, or in position of the point of 
cut-off, shall go on until the engine comes to speed, irre- 
spective of all other conditions, we shall have what is known 
as an " isochronous " governor, and shall be able to get the 
correct speed, whatever changes occur in steam pressure or 
in load, provided that there is steam enough to drive the 
load at speed with the least expansion for which the engine 
is designed. Such an adjustment can be made by substitut- 
ing the tension of a spring, properly set, for the action of 
gravity. The form of governor here illustrated is, or can 
be made to be, of this class. It simply requires that the 
spring tension shall be given a certain easily determined 
relation to the effort of centrifugal force. 

A governor of this character, when well made and 
adjusted, will open the throttle valve, or will increase the 
ratio of expansion, as the steam pressure diminishes or as the 
load is increased, and will continue to move in the proper direc- 
tion, indefinitely, or until the machine comes to speed, or 
until the engine is doing all that it can do. In the gov- 
ernor here used, two levers are set on either side the crank- 
shaft, in a frame or a pulley to which they are pivoted at 
^, b. These rods carry weights, A^ A., which may be ad- 
justed to any desired position by means of the bolts seen 
in the cut. The outer end of each rod is linked to the 
loose eccentric, C, C, by the rods, B, B, and is controlled 
by the springs, F, F, which resist the effort of centrifugal 
force tending to throw t"he weights outward. As the weights 



70 STEAM ENGINES FOR 

swing outward or inward, as the one or the other of the two 
opposing forces predominates, the eccentric is turned on 
the shaft in such a manner as to give the valves that motion 
which is necessary to produce the proper distribution of steam 




Governor. 
to bring the engine to its speed. The adjustment of this 
regulator to its work is easily obtained by the shifting of 
the weights along the levers, or by increasing or diminishing 
their amount, as is found necessary. 




o 
z 

a 

E-t 



ELECTRIC LIGHTING PLANTS. 



This governor is adjusted for an engine moving in the 
direction of the arrow. To adapt it to an opposite motion, 
the pins, b, b, are shifted to the other set of arms which are 
shown having bosses for their reception. Wooden buifers 
check the governor at the extremity of its range of motion. 

The range of expansion, as determined by the governor 
in this engine, is from the beginning up to two-thirds 
stroke. 

The engine has many interesting peculiarities of con- 
struction, in its details, which space will not permit us to 
consider, 

A licensed engineering company formerly building this 
style of engine made a form of bed whicli is somewhat 
similar to that designed by the makers of the Porter- Allen 
engine, but which is particularly solid and graceful in ap- 
pearance. It is seen on the opposite page.* This firm, as 
well as the original makers of engines built under Thomp- 
son's patents, thus tried to secure in their engines 
great weight in the parts in which solidity is important, 
such large area of bearing surfaces as is essential in these 
engines, moderately high-speed of piston and of rotation, a 
steam pressure, usually of about 80 pounds per square 
inch, and adopt a ratio of expansion for their non-con- 
densing engines, of from four to five. Their table of 
powers of their standard sizes is based upon estimates for 
steam at 80 pounds and a cut-off at one-fourth. In con- 
struction, these engines are carefully made with all joints 

* The first designer to carry the line of the steam cylinder along the surface 
of a "box-bed," and thus to secure maximum vertical and horizontal stiffness 
in this manner, so far as the knowledge of the writer extends, was Dr. E. D. 
Leavitt, Jr., who made such an arrangement in engines, in the design of which 
the writer assisted, as early as 1860. 



8o STEAM ENGINES FOR 

scraped, and all pins, and all journals also, ground with 
scrupulous care. 

The method of regulation is, as has been seen, quite 
different from that practiced by the older standard makers. 
It is subject to the objection, that as the regulator has 
thrown upon it the duty of altering the position of the 
eccentric, the load so brought upon it may make it less sen- 
sitive and less effective in regulating the speed. This con- 
clusion, which is that usually held by the older engineers 
in the profession, seems to be contrary to the fact; although, 
when comparing the older kinds of engines, it is fully sus- 
tained by the superior regulation of the engines of the " au- 
tomatic " class. The fact, now familiar to every engineer 
accustomed to the management of electric lighting ma- 
chinery, that engines having regulators of the class to which 
that under consideration belongs are capable of giving a 
good regulation, even when directly connected to the dy- 
namo, is sulhcient proof that such a system of regulation 
may be able to do perfectly satisfactory work. The fric- 
tional resistance of the system, while in motion, is not a 
matter of importance; as in any system in movement, and 
subject to jar, the friction is practically eliminated and 
every part assumes the position that it would take in a sim- 
ilar system free from friction. The action of the resistance 
of the valve, so far as it is transmitted to the regulator, 
probably acts to hold the regulator fast during the period 
of its action, leaving it free to move into any new position, 
corresponding to the speed of the engine at the instant, 
without hindrance during the remainder of the time. 

All of these fast-running engines will be seen to have 



ELECTRIC LIGHTING PLANTS. 8i 

shorter strokes of piston than is customary with the earlier 
types. One reason which has guided their designers to this 
proportion is that the loss by internal condensation becomes 
less as the steam is given less time to discharge its heat, and 
hence high-speed of rotation and short strokes are adopted. 
The best proportion of stroke to diameter of piston, the 
number of revolutions in the unit of time being fixed, is easily 
ascertained by a very simple investigation. It is found to 
be two to one. This is about the proportion generally 
adopted in these engines. Many engines are, however, given 
a ratio of i 1-2 to i. The shorter stroke has the great ad- 
ditional advantage, the speed of piston being the same, of 
giving a less costly engine to build. The proportion is 
sometimes dictated partly by the character of the work to 
be done; thus, in driving the dynamo directly, the velocity 
of rotation must be very great and a short stroke becomes 
advisable — the. shorter as the speed is higher. In such 
cases, therefore, engines are often made with even shorter 
strokes than considerations of "efficiency" alone, would 
dictate. 

Reviewing the construction of this engine, it is seen that 
it is distinguished from those which have been already de- 
scribed, by its peculiar balanced valve which can be pro- 
portioned to take any desired part of the steam pressure, 
leaving, if properly adjusted, just enough on the valve to 
hold it with certainty to its seat and to secure a little wear 
to give bearing and fit between valve and seat, that this 
valve is arranged to take steam through, and to deliver 
steam outside, the shell; that it has a system of perfectly 
flat wearing surfaces, and a positive movement of in- 



82 STEAM ENGINES FOR 

variable extent, and thus is not liable to the formation 
of shoulders on seat or valve; that its clearance is so 
small that it is easy to counteract any ill effect, ordi- 
narily due to that cause, by moderate compression; that it 
has two ports and thus possesses such advantages as may 
be claimed for that arrangement; that the governor is driven 
by a positive connection with the shaft on which it is set; 
that, as the cut-off is adjusted by the motion of an eccen- 
tric, the ratio of expansion is the same at both ends of the 
cylinder and that it possesses the advantage, common to all 
engines having a positive motion valve-gear, of being unre- 
stricted in speed. 

Many of these engines are already in use driving electric 
lighting machinery. 



THE CUMMER ENGINE. 

A LL of the class of engines now under consideration 
•*• ^ have been seen to differ radically from the engines 
previously described (as not well fitted for direct connec- 
tion to the dynamo), and to have a number of character- 
istic points in common which especially fit them for use in 
direct connection. This latter class of engines, however, 
exhibit some differences among themselves which are im- 
portant and very interesting to the engineer and the user 
of steam power. 

The engine last described will have been seen to differ, 
in a very notable way, from that which immediately pre- 
ceded it. The latter had a system of valves that differed 
from the former no less radically than did its system of 
regulation. We have now to study an engine which re- 



ELECTRIC LIGHTING PLANTS. 83 

sembles the last in its general features — the use of a cut-off 
valve riding on a seat formed upon or in the single main 
valve, a system original in principle with Meyer, an engineer 
well-known, years ago, in Europe, and the use of the pecu- 
liar form of governor which adapts itself to a position on 
a horizontal or on an upright shaft with equal facility. 
This engine, however, has some curiously interesting and 
ingeniously contrived points of construction which, as well 
as its performance, make it well worthy of attention. This, 
the "Cummer Engine," is illustrated in the engravings to 
be described below. 

The builders of this machine make a number of dif- 
ferent forms of engine, using various kinds of valve-gear 
and different forms of regulator and of engine frame ; but 
the style with which we are here principally concerned is 
that which is best adapted to driving a load at high speed 
with great economy and with the most perfect regularity. 

The general form of the engine, as shown in the Fig., on 
page 74, is very similar to that of engines already described. 
It has the "girder" frame, or bed, is well supported at each 
end, has a firm and substantial connection in the line of 
thrust and pull between cylinder and crank-shaft, and pro- 
visions for lubrication especially fitted to give safety at high 
rates of speed. A modified form of bed is seen in the next 
illustration, in which one of the engines designed for the 
highest safe speeds is shown. In this engine, the frame is 
made with a pedestal cast upon it directly under the guides 
and extending under the whole length traveled by the 
crosshead, thus giving absolute stability at the point at which 
cross strains are most severe and most productive of injury. 



86 



STEAM ENGINES FOR 



The cylinder overhangs, ansupported, at the back end of 
the frame. No support is there needed, however, as no 
appreciable vertical stress occurs there. This engine has 
the same valve and gear, and the same form of governor as 
is used in the preceding style of machine. In this latter 
form of engine, the crank is replaced by a disc, an arrange- 
ment which enables the builder to effect a more perfect bal- 
ancing of the reciprocating parts than can well be obtained 
with the ordinary form of crank. The rigidity of this form 
of engine is seen to be as essential a feature as in those 
which have been previously described. The box girder 
gives this stiffness in a very satisfactory manner. 




The Cummer Engine 



The main guides are fiat, and are fitted with removable 
faces which can be readily repaired or replaced, when worn 
or "cut," at small cost of time and money. The crosshead 
is a compact, strong casting, having bearing surfaces extend- 
ing well out under the pin, and under the piston-rod socket, 
as well, and it is therefore not likely to cause those awkward 
accidents, due to springing the piston rod at this connec- 



ELECTRIC LIGHTING PLANTS. 



87 



tion, which have proved so costly in less well designed en- 
gines. The gibs which take the wear are removable and 
adjustable. The main bearing is fitted with four-part boxes 
of babbitted cast iron, the side pieces so arranged that they 
may be set out to a bearing as they wear. All the details 
are in accordance with standard practice in this class of 
engines, and description is not called for here. It may be 
safely assumed that this is the case in any successful engine, 
as good workmanship, the best materials, and a strong sys- 
tem of connections, are essential pre-requisites to even the 
beginning of success. 




Cylinder; Steam Valves. 

The valves and the valve-gear of the Cummer engine, 
as has been stated, belong to the "Meyer system" and con- 
sist of a main valve with the cut-off valve riding on the 
back of the main. There is this difference, however, bC' 
tween the gear of this engine and others of the same gen- 
eral system : that here we find a separate system of exhaust 



STEAM ENGINES FOR 



valves which are worked independently of the steam valves, 
and thus leave the induction and eduction motions entirely 
free to be adjusted as the designer, the constructor, and 
the user, may desire. The preceding engraving shows the 
disposition of the valves in the cylinder casting, and the 
larger cuts exhibit the method of driving them. The sec- 
tion of the cylinder, above, is made horizontally through 
the steam valve chest, and shows the main valve in section, 
with the cut-off valve riding upon it. At the left is a section 
so made as to exhibit the exhaust valve seat. This is made 
removable. It will be noticed that the valves are of what 
the engineer calls the "gridiron" pattern. They are so 
made, with their several ports, to obtain a free opening with 
small movem-ent and reduced friction of the valve. The 
writer has found this device a decidedly advantageous one, 
and it has been used by some of the most successful design- 
ing engineers of his acquaintance. The more numerous 
the ports, the less the travel required for the valve, the 
smaller the steam chest space demanded, and the less the 
load on valve-gear and governor, usually. 

The next illustration represents the same parts of the 
engine as seen from the side, with valve-chest bonnet re- 
moved at one end, and a section made opposite the supply 
pipe to show the passages and valve-rods. These rods are 
driven by the main eccentric, the steam valves directly, and 
the exhaust through a rock-shaft. The cut-off valve is 
driven by a separate eccentric, as in the preceding form of 
engine, and this eccentric, like the preceding, is adjustable 
in position on the shaft by the governor. The engine is 
thus made " automatic " in its adjustment of the point of 



ELECTRIC LIGHTING PLANTS. 



89 



cut-off, and in regulation. Separate valves are seen at each 
end of the cylinder, and the "clearance" and "dead space" 
is thus reduced to a minimum. This last provision makes 
it possible to "cushion" the exhaust steam up to boiler pres- 
sure on the return stroke, and thus to secure a minimum 
waste by condensation on the opening of the steam valve 
for the succeeding stroke. Cushioning is not here limited by 
the steam side. The construction of the connecting rod, 
and the method of connection, are such that the wear of jour- 



0; 


10;"'" \ 










0) 








i" 






o". 






; 




i( 







iQJL_ 


*_ 




Cylinder; Elevation and Section. 



nals and bearings may be taken up, in any case, without 
altering, to any observable extent, the position of the piston 
in the cylinder, and this permits small cylinder clearance^ 
also. For the reason above given, the port spaces are 
made no larger than is necessary. 

A comparison of this engine with others of its class will 



go STEAM ENGINES FOR 

exhibit one very peculiar feature, in which this engine 
stood entirely alone. The governor is carried on a " gov- 
"ernor shaft " which is geared to the main shaft, and which 
has no other office than that of carrying the governor and 
the eccentrics. It is evident that so radical a departure 
from standard design must have been caused by the possi- 
bility, actual or presumed, of thus attaining some very im- 
portant result. A little study shows plainly what this 
supposed advantage must be. 

The necessity of providing for efficient performance at 
high speeds of rotation has been seen to have compelled the 
adoption of a positive motion valve-gear; the adoption of 
this gear led to the use of a powerful form of governor, di- 
rectly attached to the cut-off eccentric; this, in turn, compels 
the use of revolving weights, turning in orbits lying in the ver- 
tical plane; this last feature, in turn, again made it necessary, 
apparently,to place the governor on the main shaft, and to meet 
the effort of centrifugal force by a counterbalancing action, 
which could then only be obtained by the use of steel 
springs set in the casings of the governor. But the use of 
springs is considered by many engineers to be so objec- 
tionable, that they would submit to some expense and incon- 
venience to avoid their application, if possible. The objec- 
tions are that they are liable to changes of tension and of 
length while at work, that they never have a definite and 
calculable strength, that they are liable to break in most 
unaccountable ways, and at most unreasonable and unex- 
pected times, and that the adjustment of a balance between 
the two equilibrating forces is often difficult and almost always 
unsatisfactory. These objections undoubtedly do to a certain 



ELECTRIC LIGHTING PLANTS. 



91 



extent exist; but they as certainly are not as serious as is 
often supposed. The writer has had a long experience 




The Cummer Governor Section. 

in this direction, both in the use and in the observation 
of the steel spring for a wide variety of applicatioiis, 
and has never yet seen reason to condemn them uni-e- 



92 STEAM ENGINES FOR 

servedly. The principal objection which can be urged 
against the governor of this class, as usually adopted for the 
kind of engine now under consideration, is probably the 
fact that it cannot be reached while the engine is in opera- 
tion, and that change of speed is thus made impossible 
except by stopping the machine and making changes in the 
adjustment of the springs, then trying the speed again, and 
again stopping to adjust, until the desired speed is exactly 
attained, which disadvantage is shared by the older arrange- 
ment of governor. 

The form of the Cummer governor, which has been de- 
signed to evade these objections to the use of springs, and 
to secure certain special advantages, is shown in the above 
illustration and in that which follows. As has been seen, 
when studying the design of the engine as a whole, the 
governor of the Cummer engine is of the same general type 
as that of the engine last described; but it is mounted upon 
a shaft, separate from, and driven by gearing from, the main 
shaft. The governor shaft also carries the eccentrics, one 
of which is loose on the shaft and is controlled, as to position, 
by links from the weights of the governor as usual. The 
governor is thus enabled to shift the eccentric forward or 
backward and thus by changing its lead, to determine the 
movement of the cut-off valve and the ratio of expansion. 

There is nothing specially remarkable about this part of 
the arrangement. The position of the weights is seen to be 
determined, however, by a system of bell-crank levers which 
connect the middle point of each weight with a vertical rod 
and chain under the engine bed, and on this rod is carried 
a set of weights which may be easily reached when the 



ELECTRIC LIGHTING PLANTS. . '93 

engine is running. The bell-cranks within the governor 
casing, move a rod which passes along the centre line of 
the governor shaft and emerges at the left. This rod en- 
gages a large bell-crank at the end of the shaft, through 
which the load suspended under the engine is sustained. 
But one spring, and that a small one, is seen in the whole 
system. The centrifugal action of the governor weights, 
when at the inner limit of their range, is met by the weights 
on the scale pan, and the spring is only required to meet 




The Cummer Governor. 

the additional action of the governor weights when they 
fly outward, as the engine increases speed. The more nearly 
an equilibrium is maintained between the action of the 
flying weights and the balancing load, at the proper speed 
of engine and at all possible positions of the governor, the 
more perfectly "isochronous" does the governor become, 
and the more exactly will the engine hold its speed, under 
all variations of steam pressure and of load. With this 



94 . STEAM ENGINES FOR 



governor, the weights on the pan can be increased or 
diminished at any moment, and to any desired amount, 
whether the engine is in motion or at rest; the isochronous 
adjustment can be effected as nearly as desired, and the 
speed of engine may, at any moment be altered, much or little 
as may be advisable. 

This accessibility of the governor, and the disuse of 
heavy springs to control it, are the principal advantages of 
this form of governor. It has also some incidental advant- 
ages which are worthy of notice, although of less import- 
ance. The governor shaft is comparatively small; this per- 
mits the use of very small eccentrics; this reduces friction 
and load on the valve mechanism, and this, in turn, adds a 
little to the efficiency of the engine, as a compensation for 
the introduction of an additional shaft. The one spring 
used here is smaller than that needed for other governors 
of the same class, and is relieved from tension entirely at 
frequent intervals, and the periods of " rest " thus given it 
are likely to insure an increase in its longevity which may 
prove to be a point in its favor worth mentioning. It may 
sometimes, although certainly not frequently, occur that an 
engine may be required to work, at different times, at cer- 
tain different, but fixed, speeds. In such a case, it is easy, 
with this engine, to find a set of weights which when in 
place, will give each one of these fixed speeds; the engine 
can then be, at any instant, brought exactly to either speed 
by hanging on the scale pan the right weight for the speed. 
The several weights can be kept at hand for use as required. 
Such an arrangement may be sometimes especially useful in 
electric lighting. 



ELECTRIC LIGHT I NO PLANTS. 95 



Several styles of the Cummer engine, other than those 
which have been described, were built for the market. Those 
which have been here illustrated are, however, especially 
fitted for such work as is the subject of this article. Both 
of the forms which have been described are well adapted 
to use in electric lighting plants, and are proportioned for 
high speeds; they are designed for nice regulation and are 
likely to prove durable, economical, and otherwise satisfac- 
tory motors. They are intended for steam pressures of 90 
or 100 pounds per square inch, and their rated powers are 
based upon an assumed piston speed of about 400 times the 
cube root of stroke, as nearly as it can well be reckoned by 
the old method of James Watt — a speed more than three 
times as great as was thought best in the time of that great 
engineer. Even this speed is not to be considered remark- 
ably great for engines designed and built, as are these, with 
especial regard to the requirements of high-speed motors. 
The steam pressures adopted are those generally regarded 
by engineers as, on the whole, the best for ordinary pur- 
poses, and are those beyond which the gain in economy by 
further increase becomes rapidly less with even the best 
engines. The point of cut-off is calculated, in estimates 
of power, to be at from one-fourth to one-fifth stroke, and, 
as a rule, nearer the first than the last figure. The best 
ratio of expansion for any given case is to be determined by 
a comparison of cost of fuel and steam supply with other 
operating expenses, at the place of operation. 

The engine above described has been used, in many cases, 
to supply power for driving dynamos in electric lighting, 
and has an excellent record in that field, as well as in cotton 



90 



STEAM ENGINES FOR 



and flouring mills, which demand the most perfect possible 
regulation. 

One of these engines (16x36), at the Cincinnati Exhi- 
bition of 1883, was tested by the committee on electric 
lighting apparatus and found to alter its speed but 2^ per 
cent., when the whole load, 124 horse-power, was thrown on 
or off; it varied one revolution per minute with a change 
of steam pressure of from 90 down to 50 pounds. 




The indicator cards, of which copies are given above 
as taken from this engine, show the method of distribution of 
steam in engines with positive motion valve-gears, such as 
are here considered as fitted for direct connection with 
large dynamos, and for high speed generally. The illustra- 
tion exhibits a series of indicator diagrams taken from this 
engine at points of cut-off varying from one-tenth to one- 
third stroke. It is seen that the steam lines are as straight 
as those of a drop cut-off engine, very nearly up to the point 
at which the effect of closing the cut-off valve begins to ex- 
hibit itself in the production of the expansion line. The 



ELECTRIC LIGHTING PLANTS. 97 

expansion curve is very nearly that obtained by laying down 
the hyperbolic curve of Marriotte, and the exhaust is as 
clean and prompt as need be desired ; the back-pressure 
line closely follows the atmospheric line seen immediately 
beneath it, and the compression line at the right hand end 
of the card is quite as good as is often seen in the most per- 
fectly proportioned engine with detachable valve. As the 
steam follows further and further, the sharpness of the 
corner between steam and expansion lines gradually be- 
comes less, and the form of that part of the diagram ap- 
proximates that found in the older forms of plain slide 
valve engine. For the most generally desired ratios of ex- 
pansion, however, the form of the curve is satisfactory, and 
it is evident that the adoption of the positive motion type 
of valve-gear does not introduce any very serious loss of 
efficiency in this respect. 



THE STRAIGHT LINE ENGINE. 

T3 EVIEWING what has been said in this section of 
-*- ^ engines capable of direct connection to the dynamo, 
it will be noted that the engines which have now been de- 
scribed have belonged to two classes, differing from each 
other in two very important respects. In the first, repre- 
sented by the Porter- Allen engine, we find a form of engine 
especially, and very ingeniously, designed for high speed of 
rotation, fitted with four balanced valves, with the object of 
securing minimum " dead space," and maximum economy 
and ease of working, and controlled by a governor which 
differs from the older form introduced by Watt, by several 



98 STEAM ENGINES FOR 



useful modifications of design, and especially, by being 
loaded in such a manner that its speed, and, consequently, 
its power and sensitiveness in working, are greatly increased, 
In the second class, we find a valve-gear of the Meyer type 
driven directly by the eccentric, instead, as in the first 
class, through a link, and regulated by a governor riding on 
the main or the governor shaft, beside, and directly attached 
to, the eccentric. The features essential to a " high speed " 
engine are also embodied in the second, as well as in the 
first, class of engine. 

We now come to the examination of a third-class of high 
speed engine, which differs as radically from the two pre- 
ceeding as they from each other. In this new form of engine 
we find but a simple valve which does duty both as a dis- 
tributing an(d as a cut-off valve. A form of engine belongs 
ing to this class, with which the writer happens to be 
familiar, is that known in the market as "The Straight 
Line Engine." 

This engine, so far as it is novel, is the invention 
of, and also is designed by. Professor John E. Sweet, form- 
erly the superintendent of the workshops in which instruc- 
tion in machine work was given in the Department of 
Mechanical Engineering of Cornell University — a position 
in which he became widely known as one of the most skilful 
and ingenious mechanical engineers in the United States — 
later a President of the American Society of Mechanical 
Engineers. The first of these engines was built at Sibley 
Coiiege, Cornell University, in 1871, under the instruction 
of the designer. A second, built in 1875, i^ ^^ill in use. 

The Straight-line Engine has many interesting and novel 



ELECTRIC LIGHTING PLANTS. 



points, which will bear much more extended study than they 
can be given in the small space which can here be allowed 
for the description of the engine. The problem, proposed 
to himself by the inventor, was to design an engine which, 
while consisting of the smallest possible number of parts, 
should, nevertheless, be economical in its use of steam, 
capable of the most perfect regulation attainable with any 
known device, strong and stiff in every part subjected to the 
working strains of an engine working at high speed, inex- 
pensive in first cost, and durable as a simple engine can be. 

This engine is shown in the accompanying illustration. 

A vertical engine, which is shown at the end of the 
article, is also designed for all powers ; there seems no 
reason why it should not prove a good style for heavy work; 
better in some respects, in fact, than the horizontal engine. 

The engine takes its trade designation from its peculiar 
form of frame, which is seen to consist of two perfectly 
straight diverging struts extending from the end of the 
cylinder directly to the two main bearings, thus carrying the 
line of resistance to the pull and push of the connections 
exactly along its own central line. No possible arrangement 
could give greater stiffness with the same weight of material. 
The whole structure is carried upon three points of support, 
as is the practice with " surface plates," which must, if pos- 
sible, have an absolutely definite and invariable system of 
suports, to avoid the slightest danger of "spring." These 
points are under the main bearings, and beneath the steam 
cylinder. The two journals receive equal loads ; the crank- 
pin is not subject to the deflecting forces met with where 
a crank is overhung ; danger of unequal wear of journals. 



STEAM ENGINES FOR 



and of springing the pin, is thus avoided very completely. 
The fly-wheel is placed in twin-form between the main 
bearings, and also serves as crank, thus making the best of 
cranks as well as balance wheel. This position of the bal- 
ance wheel is one of peculiar advantage. By its action at 
this point, it intercepts heavy and objectionable stresses, 
which, in other engines, are transmitted to the main shaft ; 
and the reciprocal action of counterweights and equilibrat- 
ing parts is thus only felt within a mass of metal, which can 
resist them with perfect safety, and without their being felt 
in the more sensitive parts of the machine. This arrange- 
ment renders the main journal less subject to springing un- 
der the loads transmitted through it. To secure better dis- 
tribution of wear, the crank shaft is allowed some end-play. 
This end-play, together with the carefully arranged system 
of lubrication, are the best possible insurance against exces- 
sive friction and wear. 

The steam cylinder has the appearance of the cylinder 
familiar to every one, as seen on ordinary plain slide-valve 
engines. Its valve chests enclose separate double valves for 
steam and exhaust, and the ports and passages are carried as 
in those engines. The valve stems have no stuffing boxes, 
but pass into the chest through unusually long and carefully 
fitted holes, in a hub, made about five one-thousandths of 
an inch larger than the rod inside the Babbitt metal bush- 
ing, for a length of six diameters or more. The hub is 
loose in the hole in the end of the valve chest, and is 
packed at the ends by a washer fitted on a flat seat on the 
inside. The piston-rod is similarly fitted. 

The crosshead is a very long casting which overruns the 



M 




ELECTRIC LIGHTING PLANTS. 105 



guide at each end at every stroke, and thus is rendered safe 
against wearing to a shoulder. A pin subject to recipro- 
cating efforts in any part of an engine, whether it rotates, or 
carries a rotating or a vibrating piece, is apt, in time, to 
show wear on the two sides in line with the principal pull 
or thrust, and to lose its cylindrical form. In this engine, 
such wear is avoided at the crosshead pin, by cutting away 
the surfaces, which do little or no work, and thus securing 
overrunning surfaces, which are not subject to this distorted 
wear to so great an extent. Many other minor points invite 
attention, but they cannot be here considered. 

The principal feature of this design, in connection with 
that phase of its work which is of especial interest here, is 
its valve-motion. The valve is a rectangular block, sliding 
between the seat and acoverplate; is shown in the engraving. 
Ports are cut through the coverplate, through the valve, 
and through the seat into the steam and exhaust passages 
in the cylinder casting, in the proper positions. These ports 
are double at the ends of the valve, and a single port of 
ample area is made through the middle of the valve. 

This valve is what may be called a " piston valve " of 
rectangular section, the space in which it slides having, 
therefore, also a rectangular section, and permitting the use 
of a detached coverplate, which, while sustaining the pressure 
of steam that would otherwise come upon the valve, 
and thus making it a balanced valve, nevertheless allows 
any unusual pressure, occurring when the piston comes 
back to the compression period of its cycle, to raise it, and 
thus to permit the water which may have caused the pressure 
to flow back, and thus relieve the cylinder, and obviate all 



Io6 STEAM ENGINES FOR 

danger of forcing out the heads. The principal feature of 
this device is not new ; the writer handled such a balanced 
valve on marine engines, rated at above 5,000 horse-power, 
nearly twenty years ago, and found them, so far as his own 
experience went, perfectly satisfactory. This new applica- 
tion of the principle, however^ embodies some new and 
interesting points. The valve cover is sustained on loose 
packing strips, which are free to close up upon the edges of 
the valve, and to take up wear as it occurs. The form of 
the plate, its domed top, is such as to give it great stiffness 
against the superincumbent pressure, and thus to prevent 
pressure on the valve itself in consequence of spring in the 
plate, and the ports are so placed as to prevent the cutting 
away of the faces and seats by the rushing currents of steam. 
The valve and cylinder ports are not dressed out ; the 
casting is made so accurately that these edges can be left as 
they come out of the sand without loss of efficiency in the 
working of the valve. 

The valve is driven by an eccentric, the motion of which 
is controlled by the governor, and the connection of which 
with the valve is effected by the peculiar system of linking, 
seen in the preceding illustration. The eccentric is so sus- 
pended from the disc, to which it is attached, that it may 
be thrown across the shaft by the action of the governor, in 
such a manner as to give the effect of the once common 
and well known " Dodd motion." It is carried on a lever, 
which is pivoted at one side of the shaft, while the governor 
rod is attached at the opposite side. The singular positions 
of the eccentric rod and the rockshaft arm enable the 
alteration of the throw of the eccentric produced by 



•\ 



ELECTRIC LIGHTING PLANTS. log 

the governor, to be effected without alteration of the 
lead of the valve, so that the steam may be admitted, at all 
times, at the same point in the revolution of the engine. 
This it does, since the line of the eccentric rod is, at the 
commencement of stroke, in line with the lever on which the 
eccentric is carried. 

The governor is similar, in principle, to those which have 
been described as used on the last type of engine. It con- 
sists of a single weight, or ball, carried on the end of a lever 
which is pivoted, near its middle point, on one of the arms 
of the governor pulley, and connected to the spring, by 
which it is held under control, by a strap extending across 
to the other side of the shaft to the end of the spring, which 
is there secured to the rim of the pulley. The action of 
the governor is substantially the same as that of those which 
have been already described. When the speed decreases, 
the tension of the spring, at the end of the weight lever, over- 
comes the centrifugal effort of the ball, and the latter is 
forced in toward the shaft, carrying with it the end of the 
eccentric lever, and thus giving the valve greater throw, and 
extending the period through which the steam follows the 
piston, producing more power and bringing the engine up 
to speed. The reverse change of speed of engine produces 
the opposite action of eccentric and of valve motion, and 
the cut-off is shortened, and the power of the engine is re- 
duced to that needed to give the correct speed. As this 
governor may be made as nearly isochronal as may be de- 
sired, the approximation to correct speed may be made as 
close as is consistent with the sensitiveness considered per- 
missible. The use of a single eccentric and of a single gov- 



STEAM ENGINES FOR 



ernor ball, and the general simplicity of this combination, 
are especially pleasing to the engineer. They, however, 
include the use of a simple valve, and thus restrict the de- 
signer, somewhat, in his adjustment of the steam distribu- 
tion, a restriction which the more complicated forms of 
valve-gear are constructed to avoid, as it is well understood 
that the economy of the machine, in its use of steam, is to 
a certain extent, dependent upon the method of distribution 
of the steam entering, and of the exhaust leaving the cylin- 
der. The main objection is the fact that the mean pressure 
of the steam entering the cylinder up to the point of cut-off 
is necessarily less with a single valve than with the gear in- 
troduced by Sickles and Corliss, and their successors, and 
which have been long standard, and which are admittedly 
superior in this respect. . Whether the more costly, but 
more efficient gear shall be used, is to be determined partly 
by the cost of fuel, and must be settled by the judgment of 
an experienced engineer in each individual case. 

The difference in this respect is not, however, as great 
as has been by some engineers supposed, and the econom- 
ical value of heavy compression is now becoming so well 
understood, that the general impression in regard to this sys- 
tem of valve motion is becoming considerably and rapidly 
modified. What is lost by the drop of pressure between the 
boiler and the piston, is partly compensated by the variable 
and automatically adjusted compression obtained with this 
kind of motion, as is well illustrated in the action of the 
Stephenson link as used on the locomotive. With this 
arrangement, there is also some loss at the exhaust period, 
but not usually enough to be considered serious. As this 



ELECTRIC LIGHTING PLANTS. 113 

particular engine is operated, this latter loss, and possibly, 
to a slight extent, the former, are somewhat reduced by 
setting the valve without lead, or even with "negative lead," 
/. e. so that the engine does not take steam until the crank 
has just passed the center, and the piston is starting on the 
forward stroke. 

The engine, as a whole, with all its important parts in 
section, is shown in the above engraving. The unusual 
quantity of material as compared with earlier practice in 
older forms of engine, the excellent distribution of that 
material, the small number of parts, the heavy crosshead, 
the arrangement of fly wheels, and the form of valve are all 
plainly seen, as well as the general arrangement and system 
of connection. The rods and pins, and all running 
parts, are made of steel ; journals are ground to perfect form 
and polished, and the engine, when completed, is set up in 
the shop and carefully tried before sending it out, as is 
becoming the custom with good builders everywhere. The 
designer has made a special effort to reduce friction to a 
minimum, and has given the engine easy running piston and 
crosshead, perfectly formed journals, and a valve gear and 
governor, which are as nearly frictionless as those parts can 
well be made. The growth of the engine into its present 
shape, from the first crude sketches made in 1869, to the 
finished engine and completed type of to-day, and especially 
the gradual evolvement of the governor and valve gear from 
the older forms, would be an interesting subject of study, 
but it cannot here be undertaken. The survival of the fit- 
test, among these devices, has led to the production of the 
engine above described. 

The Straight Line Engine has been frequently applied 



1 14 STEAM ENGINES FOR 



to the driving of electric lighting apparatus. In Pen- 
ney's arrangement of a station of 120 lights, the 
connection of power to dynamo is effected through 
friction clutches, which may, at any instant, be thrown 
out or thrown in ; any two of the engines have ample 
power to drive all three of the dynamos used, and a reserve 
is thus supplied to be used in case of the necessity of 
throwing off one engine for repairs. The current from 
any one generator is capable of being switched into any 
circuit, and all parts are accessible for examination and 
repair. A novel device is that of placing the driving pulleys, 
on the main line, on separate hollow shafts, independently 
supported, to prevent the springing of the line shaft by 
the pull of the main belts. The line shaft runs directly 
through the jack shaft, carrying the driving pulley on 
the line. 

As this engine is adjusted, with large compression when 
at regular speed doing the rated work, with negative lead on 
the valve at that point, becoming positive lead at ^ cut-off, 
it illustrates well the efficiency of the class. A 50 horse- 
power engine, driving a 40 light dynamo, according to 
the report of the manager at the station, ran at 219 revolu- 
tions, and at 220 when 27 lights were thrown off. The 
writer, testing one of these engines rated at thirty-five 
horse-power, using a Prony brake to take up the 
power, counted 233 revolutions, light, and 232, loaded 
with above forty horse-power ; with lower steam, the 
figures became 231 and 230. A well-balanced valve 
and a nearly frictionless governor are the elements giving 
success here. Every good engine, driving dynamos, is 



ELECTRIC LIGHTING PLANTS. 



IIS 



expected to rival this, doubtless, but, doubtless many do 
not. The simple-valve engine can evidently, as is here 
seen, be made, by a skilful engineer, to do excellent work. 




Vertical Straight Line Engine. 



lf6 STEAM ENGINES FOR 



IV. 
Engines Capable of Direct Connection. — {Continued.) 



THE ARMINGTON AND SIMS ENGINE. 

THE engine last described, and that to be here examined, 
are the result of an attempt on the part of their design- 
ers to secure a form of engine which should not only be so 
proportioned and so arranged in the disposition of their 
details that they may be driven up to the speeds of rotation, 
now so frequently found desirable, without excessive jar, 
serious wear, or dangerous heating of journals, but which 
should also be so simple in plan, so inexpensive in construc- 
tion, and so easy of repair, that the cost of maintenance, 
that great tax upon the proprietor of the average steam en- 
gine, should be reduced to the lowest possible figure. 

In these engines, the possibilities in the direction of in- 
creasing speeds, are sought to be made the most of. Their 
market is not only to be found in the domain of the electrical 
generation of light, and electrical transmission of power, 
but in older fields of work as well. The loss of power in 
the "jack-shafts," or "first motion shafts," of mills and 
workshops driven by the low-speed engines is an item of 
no inconsiderable amount in many cases. The tendency 
is now observable toward the adoption of the high-speed 
engine, even where not quite as economical in the use of 
steam, in direct connection with the main line of shafting, 
through the intermediary of a single belt or pair of gears, 
or even by directly attaching the crank-shaft of the engine 



ELECTRIC LIGHTING PLANTS. iig 

to the main line by a coupling. Many flouring mills and 
several rolling mills to the personal knowledge of the 
author, have been operated in this way for some years, and 
the system will probably become rapidly more general. 
In this country, the use of gearing for such connections has 
long been almost entirely superseded by the introduction of 
belting. The smaller first cost, the diminished noise, the 
lessened danger which accompanies their failure, and other 
obvious advantages, have been found to far more than 
counterbalance the cost of maintenance of the belt. By 
thus connecting directly to the main line, also, the cost of 
belting is greatly reduced. As the speed of shafting is 
rarely less than 150, and seldom more than 250, revolutions 
per minute, it is not difficult or objectionable to establish 
this method of connection. The same advantages are then 
derived that are experienced in the direct connection of 
the engine to the dynamo-electric machine. The total first 
cost of power is thus often reduced thirty and sometimes 
50 per cent. As has been already intimated, there seems 
to be no nearly reached natural limit to the increase of 
engine speeds, except the practical limit of perfection of 
workmanship and excellence of materials, which limit is 
being constantly pushed farther and farther back, as the 
demands upon our engineers and mechanics are more and 
more exacting. President Westmacott, of the British In- 
stitution of Mechanical Engineers, has remarked that, at 
the high speeds (400 to 500 revolutions per minute) attained 
by the screws of Thorneycroft's torpedo boats, the engines 
seemed to run more smoothly than at lower speeds. This 
has been noted by every builder, and every driver of fast 



STEAM ENGINES FOR 



engines. The author, in handling naval screw engines of 
short stroke and high speed, has frequently observed this 
fact, and, after a somewhat wide range of experience with 
engines of long and of short stroke, of from 15 to 500 revo- 
lutions, and of powers ranging from the toy engine built 
during his hours of leisure when a boy in a short jacket, to 
marine engines rated at above 5,000 horse-power, at sea 
and on shore, in the mill and the workshop or on the loco- 
motive, he has never yet seen evidence pointing to any as 
yet nearly reached limit to engine speed, except that which 
is imposed by such conditions as we are gradually and 
steadily modifying, as our knowledge and skill become 
more nearly able to cope with the difficulties which arise in 
our constantly changing practice. 

It will have been observed that, in all the engines which 
have been here described as adapted to direct connection 
to the dynamo and to the "first motion" shaft, some form 
of balanced valve has been used. It has been seen that one 
of the conditions of good regulation by a governor, v/hich 
determines the "point of cut-off," is that the work thrown 
upon the governor shall be the least possible. This con- 
dition evidently points to the use of some expedient, in 
cases in which a positive-motion gear is used, by which the 
resistance to motion of the valve, while a change is being 
effected by the ^'governor, shall be made a minimum ; this 
evidently indicates the advisability of adopting some form 
of balancing device. 

The engine to be here described has been designed with 
this end in view, as well as with the idea of securing a form 
of anachine which should be simple and inexpensive to 



ELECTRIC LIGHTING PLANTS. 121 

build, and to keep in repair ; prompt and exact in regula- 
tion under sudden variations of load, and as nearly isoch- 
ronous in its governor-motion, as is practicable. It is of 
the same general class with the last several described forms 



Governor and Eccentrics. — Minimum Throw. 

of engines, but differs from them in its details and in its pro- 
portions, somewhat, and, especially, in the form of its valve, 
and in the devices intermediate between governor and 
valve. In this engine, the "piston" valve is used, com- 
bined with a double port, such as was first used by Allen in 
the locomotive slide valve. These details are illustrated 
further on. The engine, as a whole, will be first described. 



STEAM ENGINES FOR 



The accompanying engraving present two perspective 
views of the Armington & Sims Engine, of the styles com- 
monly used in driving electric light machinery. The bed 
is seen to be of the kind already described in the account 
of the Porter- Allen engine, heavy, solid, stiff, yet neat, and 
even graceful, taking the bending stresses of the guides at 
its upper surface, and insured against twisting strains by the 
box form of its section. Two main pillow blocks, in the 
first engine illustrated, carry its steel crank-shaft, and sup- 
port the two wheels, one of which is a balance wheel, and 




Crank-pin and "Wiper." 

the other of which is the pulley, from which the engine is 
belted to its work. The steam cylinder is overhung, and 
the exhaust pipe is carried down below the floor, clear of 
the foundation, which latter has a minimum extent, and 
cost, while amply heavy, and is long and strong enough to 
carry the engine steadily. In some cases, the frame is made 
with but one pillow block, and the crank is overhung ; the 
plan here illustrated is, however, a better one when the en- 
gine is to be driven up to the now usual speeds of such 
machines. 

The journals are all large, and carefully calculated for 
the speeds and pressures adopted. The designers make use 



ELECTRIC LIGHTING PLANTS. 1 2 5 

of a method of calculation introduced some years ago, by 
the author, which is based on the working of marine and 
stationary engines, under his own management, or under 
his own observation. The drain-pipes for the cylinder are 
fitted as usual, but should be rather larger and more care- 
fully planned, than is necessary where the engine has a 
valve, which may lift from its seat should the boiler at any 
time 'prime" or "foam," and send water over into the 
cylinder with the steam. The provision for lubrication is 
a matter of vital importance in all engines of this class. In 
this engine the "sight feed " is used, in which each drop oi: 
oil falls through a clear space, on its way to the point to be 
oiled, in full view of the man in charge, and any failure of 
the oil to "feed " is thus promptly detected. The crank- 
pin is supplied by a " wiper " (see Fig.), which takes its 
supply of the lubricant from the oil-cup at every revolution 
of the crank. This device has been used, in very similar 
form, by the author, on fast marine engines, with perfect 
satisfaction, and it is found to work well here. 
' The two large engravings show opposite sides of the en- 
gine, and the second exhibits the arrangement of a single 
wheel, and of the steam-chest and valve mechanism. As is 
here seen, a governor, of the same type as that exhibited in 
the articles describing the " Buckeye " and the " Straight 
Line " engines, is secured to the arms of the pulley on the 
nearer side of the frame, and is arranged to adjust the 
position of the eccentrics, which give motion to the valve 
through a rod and valve stem, the connection between 
which two parts is made at a point at which they can be 
conveniently supported by a rockshaft and arm carried at 



126 



STEAM ENGINES FOR 



the middle of the length of the frame. The cranks are, as 
seen in both illustrations, two discs in which the balancing 
mass can be secured at any desired point. The width of 
the pulley carrying the main belt is sufficient to take a belt 
of such breadth, that the stress shall be about 35 pounds 
per inch of its width. The main bearings are made with 
boxes set at an inclination to the horizontal, and provision 




Section of Cylinder. 



is made for taking up wear. The crank-pin is of steel, 
ground carefully to size, as is the universal practice among 
good builders of this class of engines. In this machine the 
main journals are also ground. The distance between main 



ELECTRIC LIGHTING PLANTS. 127 

bearings is made as small as possible, to permit high speed 
with little risk of springing the shaft. The front cylinder 
head can be removed, when necessary, as shown in the next 
illustration, independent of bed and cylinder alike. 

As here shown in section, it is seen that the cylinder, 
steam-chest and valve-seat are all in one casting, which is, 
however, not a remarkably intricate one. It is best shown 
by the perspective view, while the section next given will 
afford a better idea of the arrangement of the valve. 

The steam-chest, S, S, is in direct communication with 
the boiler, and the valve, which is of the piston form with 
a double steam-port (the second port being seen at P, P ), 
is surrounded by the "live steam," thus taking steam at the 
middle and exhausting it at the ends of the chest, at E, E. 
The valve moves precisely as does the ordinary locomotive 
slide valve, and, as here shown, is just taking steam at the 
piston end of the cylinder, both directly past the shoulder 
of the valve and through the secondary port at the oppo- 
site end of the valve. Thus the steam is introduced, at the 
beginning of the stroke, through a double length of port, 
and hence, with unusual promptness when the engine is 
running at high speed. The consequence is that it gives 
approximately boiler pressure in the cylinder, and through- 
out the stroke up to the point of cut-off, if the steam pipe 
is short and direct, the steam line on the indicator diagram 
is very nearly perfectly horizontal and straight from end to 
end. This is a very unusual feature in diagrams from en- 
gines having positive-motion valve-gear. The form of this 
valve is well shown in the accompanying engraving, which 
exhibits the valve apart from its casing. 



1 2 8 STEAM ENGINES FOR 

All engines of this class will have been seen to be re- 
markable for the shortness of their stroke of piston, as 
compared with the diameter of cylinder. The section of 
the cylinder just given, shows how advantageous is this 
proportion in enabling the port-space to be reduced to a 
comparatively small volume. In the engine of long stroke, 
the port-space becomes seriously large and the compression 
required to fill it introduces a considerable loss both of 
power and efficiency, if the valve-gear used is of the type 
here seen. In fact, it would be probably quite impractic- 
able to secure such a steam distribution as would satisfy 
the majority of engineers, were the engine of long stroke 
and a single valve adopted moved by a link, or by such an 
equivalent for the link as is here used. The total " dead 
space" in these engines, including piston-clearance, is 
sometimes as low as 5 per cent, on large sizes. In all cases 
compression fills this space at every stroke. The piston- 
valve has been often used by earlier builders, but that here 
shown possesses a novelty in the double port. Its advan- 
tages are the ease and cheapness with which it can be made 
and fitted, and with which it can be replaced when worn, its 
perfect balance and ease of working under any practicable 
steam pressure, its permanence, tightness and remarkable 
durability when properly cared for and used with boilers 
supplied with good water. Its disadvantages are, the ra- 
pidity with which it sometimes wears, when it is not kept 
well lubricated, or when it is exposed to the action of steam 
carrying over from the boiler acidulated or dirty water, the 
danger of injury to the cylinder or its heads when priming 
occurs, and the proneness of the attendant to neglect its 



ELECTRIC LIGHTING PLANTS. 



129 



repair when it requires such care These disadvantages 
have sometimes proved to be so serious, as to give many- 
engineers a very strong prejudice against the valve ; on the 
other hand, this unfavoi^able prejudice seems to be now 
giving place to a decidedly favorable opinion, assuming that 
the valve is well made and is to go into good hands, and to 
be used under proper conditions, and these and some other 
very successful makers have definitely adopted the piston 
valve as a feature of their standard designs ; it is even 
coming into use in marine engines of the largest size. In 




Armington & Sims Valve. 



the engine here under consideration, the valve is said by the 
constructors to have proved eminently successful and to 
have proven more durable than their earlier constructions, 
in which they adopted a balance flat valve. It is probably 
too early, as yet, to fully decide what are the exact relative 
merits of the two kinds of valve. In this particular case, 
the removal and replacement of the piston valve can be 
done quickly and inexpensively, and a spare valve being 
kept on hand, it is probable that its use may prove econom- 
ical and satisfactory even where the water used for the 
boiler is not of the best. 

One of the most important, novel, and beautifully ingen- 



130 



STEAM ENGINES FOR 



ious details of this engine, is its peculiar arrangement of 
governor and eccentrics. These parts are exhibited in two 
engravings. 

The regulator is precisely the same, in principle, as those 
already described as adapted to the adjustment of the 
eccentric on the main or the governor shaft. It has the two 
weights, I, I, carried on, and forming a part of arms piv- 




Armington & Sims Governor and Eccentrics. — Maximum Throw 



oted to the governor pulley, and revolving in the vertical 
plane as usual in that class of governors. The position of 
these weights, as determined by the speed and the action 



ELECTRIC LIGHTING PLANTS. 1 3 1 

of the springs, determines the position of the eccentrics, C, 
D, and thus the position and motion of the valve, and the 
point of cut-off, flying out and giving a higher ratio of 
expansion as the load on the engine is diminished, or as 
steam pressure rises in the slightest degree, and a lower 
ratio as these conditions are reversed. In the device here 
adopted, however, the valve is driven by an eccentric 
which is " duplex." One eccentric, C, is set inside another, 
D, and connected to the governor arms in such a way 
that, as the weights separate with increasing speed of en- 
gine, both eccentrics are turned on the shaft so as to cause 
their "throws" to coincide, or to separate, as may be 
necessary. When they coincide, the travel of the valve is 
due to a greater total throw, B, and is a maximum ; when 
they are separated as far as possible, the throw becomes A, 
and the travel is reduced to a minimum. The action is 
almost precisely the same as that of a " Stephenson-link," 
worked between full and mid-gear. When the two eccen- 
trics give maximum travel, the action is that of the link- 
motion in full gear ; when they are at opposite sides of the 
shaft, the action is that of a link in mid-gear. By setting 
them at intermediate points, the throw is made that is requir- 
ed to give an intermediate action of the valve, and thus the 
distribution of steam is made to accord with the demands 
of the work by such a variation of the ratios of expansion 
and of compression as is obtained by the link-motion, and, 
in this case, with the advantage in promptness of opening 
and of closure obtainable with a double-ported valve. The 
range of action given in this engine is sufficient to permit a 



1 3 2 STEAM ENGINES EOR 

range of cut-off from o to about three-quarters stroke. The 
lead remains unchanged, and the compression increases as 
the ratio of expansion is increased. 

The springs of the governor are used in compression. 
The distribution of steam at the usual speed, and with full 
load, is shown by the accompanying illustration, which is a 
copy of an indicator diagram taken from one of the engines 
driving the large dynamos at the Edison station in New 
York city. These engines are coupled directly to armatures, 




Diagram Taken at the Edison Station. 

and make with them 350 revolutions per minute. One of 
these engines was recently kept at work 17 days, making 
over 8,400,000 revolutions without stopping, and then was 
not stopped because of any difficulty with the engine. 
When examined by the author, they were doing their work 
steadily and smoothly, and were not appreciably affected 
by the sudden changes of load produced by throwing on 
and off any considerable proportion of the lights on the 
circuit. 



ELECTRIC LIGHTING PLANTS. 1 33 

This engine illustrates well the perfection of regulation 
attainable by these positive motion valve-gears attached to 
this form of governor, to which attention has already been 
called. At a trial of engines of this make made by the 
author, to satisfy himself in regard to their action under 
varying load, 25, 50, and sometimes 60 Thomson-Houston 
arc lights were thrown on or off, and the variation of speed 
was but one and two revolutions, respectively, in 280. No 
special preparation or adjustment was allowed in this case, 
and there is no reason to doubt that still closer regulation 
and more perfect isochronism are attainable, if they, at any 
future time, should prove to be desirable. These engines, 
^Yt, by 12 inch cylinders, had never been before tested, and 
had done no work until started under the direction of the 
author. The lamps demanded very exactly 0.7 horse-power 
each, a fact which indicates that, as connection is there 
made, there can be but little lost power between the engine 
and the lamp. The form of card under load is seen below. 




Diagram Taken from A. & S. Engine. 



134 STEAM ENGINES FOR 

The success here obtained in the use of a single valve is 
as encouraging as it is remarkable. While it can hardly be 
expected that the economy of this system, other things be- 
ing equal, can be fully up to that obtainable with the more 
elaborate forms of valve-gear previously illustrated, there is 
no question that it is so great that these simple forms of 
engines will be able to find a market in that very wide field 
in which their extreme simplicity of mechanism and their 
moderate cost, as well as their successful operation at high 
speeds, are qualities which compensate any such differ- 
ences in cost of the steam supply. If the same distribution 
of steam, and the same economy is obtained with the one 
form of valve motion as with the other, and if, as is the 
case to a very satisfactory degree with these engines, a cor- 
rect form of indicator diagram can be obtained, it is to be 
expected that the engine will be economical in its use of 
steam. The increasing compression here noted with in- 
creasing expansion is a decidedly advantageous feature, as 
it has an important influence in checking losses by " cylin- 
der condensation" at high ratios of expansion, while also 
reducing the waste due to large clearance spaces, where 
such exist. 

Every engine and every machine of importance, or re- 
markable in any respect, as in such a combination, of in- 
genious devices, effective combination, and efficient opera- 
tion as is here illustrated, is, invariably, the outcome of a 
long period of progressive invention, unintermitted experi- 
ment and more or less steady growth from an initial stage 
to its condition of successful adaptation to the demands 
which it is especially fitted to meet. The Armington & 



ELECTRIC LIGHTING PLANTS. 



Sims engine is no exception to the rule, and its inventors 
and makers, as has been seen, are fortunate in having been 
able to reap so satisfactory a harvest after so long, a period 
of growth and ripening. The engine is now built, not only in 
the United States, but in Canada, Great Britain, France 
and Austria. This American engine is in use on many 
foreign steamers, and in numbers of European buildings, 
public and private. It drives the dynamos in the British 
Houses of Parliament. 



i3f> STEAM ENGINES FOR 

V. 

Fast Engines of Peculiar Design. 



BALL S DYNAMOMETRIC GOVERNOR. 

THE forms of steam engine which have been described 
in the preceding articles have been chosen as being 
fairly representative of what may be termed standard types 
of engine as built by makers of reputation. It will be seen 
that they present to the student of the steam engine several 
distinct forms of machine, each of which is now acknow- 
ledged to be well adapted to produce a certain result in the 
application of heat energy, through the medium of steam, 
to the production of power, and that each is especially fit- 
ted to do its work under certain definite conditions, which 
conditions are less completely met by the others. Each is 
well-known in the market as an engine which has taken its 
place among those which have passed the experimental 
stage and may be relied upon to do good work if well built 
and put in operation under the conditions that it is designed 
to meet. They embody ideas and inventions which have 
grown into form during years of experiment and faithful 
trial and the variety of makes to be found in the market 
belonging to each class, and differing only in the design and 
construction of details, proves that the main principles 
upon which each class is based are well established and 
sound. 

The engines now to be examined are distinguished by 
certain peculiarities of design and construction which mark, 



ELECTRIC LIGHTING PLANTS. 



^n 



in some cases, new departures, in other cases, peculiar ways of 
reaching the end at which more familiar devices were aimed. 
It has been seen that the regulation of the steam engine 
has been found to be one of the most important matters to 
which the attention of the engineer has been called. For 
many purposes, the uniformity of motion of the engine is 
an even more important quality than its economy in the use 




The Ball Engine. 



of fuel, or in all running expenses. A slight change of 
speed in an engine driving dynamo-electric machine will 
seriously injure the value of the light, in nearly every loca- 
tion, and may sometimes entirely destroy it ; a moderate 
variation of speed in the motor of a cotton mill making fine 
goods may break more threads in the spinning department 



138 STEAM ENGINES FOR 

or do more injury in the weaving room, than would be 
compensated by the difference in economy between the 
most efficient " automatic" engine ever made and the most 
wasteful engine in the market. The principle of regulation 
of the steam engine has been, from the time of the applica- 
tion of the old " fly-ball" governor to the Watt engines of 
a century ago to the present day, that of making the speed 
of the engine determine the amount of steam that shall be 
supplied to it. In the first engines used in the driving of 
machinery, in the old " Albion Mills" erected by Watt and 
his partners in London, in 1786, and for 50 years afterwards, 
the governor adjusted the supply of steam by moving a 
throttle valve. The governor was next arranged to deter- 
mine the point of cut-off by Zachariah Allen, of Providence, 
R. I., in 1834, and by George H. Corliss, in 1849, to adjust 
the trip of his detachable valve-gear. From this latter date, 
it has been the universal custom to so apply it in all engines 
in which uniformity of motion and economy in the expen- 
diture of steam were the controlling considerations in their 
design. The method of accomplishment of this result has 
been seen in the preceding pages, as practiced by Corliss 
and Greene, and by the constructors of positive-motion 
gears which have been the later outgrowth of modern 
changes in the application of steam power. 

Now, after half a century since the grand step taken by 
Zachariah Allen has passed, and a generation after that 
taken by Corliss, a new principle has been introduced into 
the construction of the steam engine, viz., the control of 
the speed of the machine, so far as it is due to the varying 
load, by that variation of load, making the cause of the irre- 



ELECTRIC LIGHTING PLANTS. 139 

gularity of motion its own corrective, and placing the regu- 
lating principle between the work and the engine in such a 
way that the latter may be made to preserve any given speed 
with perfect uniformity, so far as it depends on the load, or 
causing the speed either to be increased or diminished to 
any desired extent by any given variation of load. 

This idea, like all valuable inventions, has not been the 
result of a single thought or the product of a single brain ; 
it has been floating in the minds of thoughtful engineers for 
a long time. It was proposed to the author, by one of the 
generation of inventors just passed away, years ago ; but, 
in its present form, it became practicable only after the in- 
troduction of the high-speed engine had permitted the use 
of the form of centrifugal governor seen in the engines last 
described. The engine about to be considered embodies 
the first practically useful application of this principle, in a 
practically successful form of engine. 

The Dynamometrically Governed Engine is the invention, 
so far as it differs essentially from other engines of its class, 
of Mr. F. H. Ball, of Erie, Pennsylvania. In its general 
form and in the details of construction, generally, it resem- 
bles the last two engines which have been described. It 
has a single-valve, positive motion valve-gear, and the solid 
compact structure characteristic of all the so-called high- 
speed engines. The accompanying illustration will give a 
correct idea of its form and proportions. 

The engine bed is of strong and stiff construction, and 
very similar to others with which the reader has become 
familiar. The steam-cylinder is overhung and bolted to a 
faced flange as in the Porter-Allen engine. The main pil- 



140 STEAM ENGINES FOR 

low blocks are set in the bed of which they form a part, and 
their caps are placed at an angle with the horizontal plane, 
as is sometimes done in marine engines, and less frequently 
in stationary engines. The system of boring the seat for 
the cylinder, aligning the guides for the cross-head, and 
boring out shaft-bearings, here adopted, gives perfect align- 
ment ; and the preservation of the alignment is insured by 
this unification of parts formerly detached. As is the case 
with all good engines, the fitting parts are made to standard 
gauge, and a system of inspection insures good work. Pack- 
ing is dispensed with, and joints are made tight, by securing 
exactly plane, and perfectly smooth, surfaces, at abutting 
points. The wearing surfaces of the valves, and other 
rubbing parts, are scraped to shape and exactness of form, 
by the aid of surface plates. The valve is made tight un- 
der steam-pressure, the form of the valve being such as to 
permit this rather unusual operation. 

The Ball Engine has a short stroke and high speed of 
rotation, ranging as now built, from 7 to 10 inches diameter 
of cylinder, 10 to 12 inches stroke of piston, and making 
250 to 350 revolutions per minute. These proportions are 
adopted, probably, principally with a view to meeting the 
demands of electric lighting. 

The essential and most peculiar feature of the Ball en- 
gine, and that which gives it a place in this little treatise, 
is, as has been already stated, its governor. 

The Ball Governor is, in the main, like the governors 
which have been described as controlling the several engines 
which have been immediately herein before described. It 
consists of a " governor-pulley," from the arms 'of which 



ELECTRIC LIGHTING PLANTS. 141 

are swung a set of weights, which are arranged to move in 
the plane transverse to the shaft on which the pulley is car- 
ried. These weights, or balls, are restrained from moving 
outwards, under the influence of centrifugal force, by a set of 
strong steel helical springs, secured, at one end, to the balls, 
and at the other, to the rim of the pulley. Any movement 
of the weights, in either direction, causes a motion of the 




The Ball Governor. 

eccentric, resulting in the alteration of the throw of the 
valve in such a direction, and to such an extent as to bring 
the engine very exactly to speed. To this extent, the Ball 
governor is identical, in its general construction and in its 
principles and mode of action, with those already familiar 
to the reader. To this extent, it is possessed of the same 



142 S TEAM ENGINES FOR 

qualities as the others of its class, and it has been seen that 
good workmanship and correct proportions and adjustment 
may give wonderful nicety of regulation. 

To this governor, as commonly built, Mr. Ball adds a re- 
markably ingenious, and singularly simple yet perfect, in^ 
vention ; it is exhibited in the accompanying figures. The 
first of these illustrations shows the governor-pulley detach- 
ed from its shaft, and does not show the eccentric; 
it presents only the essentially novel part of the 
device. 

It is seen that, attached to the radius-bar of each ball, is 
a small spring, connecting a point near the fulcrum of that 
lever with the extremity of a strong, peculiarly shaped arm, 
projecting from the hub on the shaft which is seen within 
the hub of the pulley. The governor-pulley is set loosely 
on this inner hub, which latter is keyed fast to the shaft. 
The arrangement is evidently such that, the shaft being 
turned by the engine, the effort must be transmitted 
through the small spring to the weight arms, thence to the 
pulley, and from the latter to the load to be driven, through 
a belt carried on that pulley. The effect of this curious 
disposition of parts is easily seen : Suppose the governor 
to be so adjusted that, at normal speed and under the rated 
load, the supply of steam and the distribution of that steam, 
are precisely correct, as intended by the designer of the en- 
gine. Now, if a variation of steam-pressure should occur, 
the governor at once meets the consequent change of speed 
by a corresponding change of steam-distribution, and the 
variation of speed is restricted to a range, which, if the 
governor is well proportioned and well adjusted, may be 



ELECTRIC LIGHTING PLANTS. 143 

quite imperceptible to the senses, and hardly measurable 
by count. 

This governor here acts like all the others. But, sup- 
pose the steam pressure to be unchanged, and the load to 
vary — we now have a new movement introduced. The 
force exerted in driving the load is transmitted through the 
small springs which are peculiar to this governor, and 
which connect the main shaft to the driving pulley, through 
the governor. The instant that any relaxation, or any in- 
creased tension, is felt here, the relaxation or the extension 
of the springs, so produced, causes a change in the position 
of the weight-arms, and a corresponding alteration in the 
position of the eccentric ; and the steam supply is at once 
readjusted to meet the variation of load. This may be 
done so promptly and so exactly, that, however much the 
load may vary, the speed of the engine remains precisely the 
same. I^oad may be thrown on and thrown off to any extent 
that may be found desirable or necessary, and the engine 
goes on with its fluctuating task without an instant of visi- 
ble change. Should both steam-pressure and load vary at 
the same time, the load. strings set the example of changing 
the steam distribution to meet the new conditions, and the 
governor-springs controlling the balls are immediately seen 
to yield to the effect of the varying steam-pressure, and to 
continue their motion until the flying weights have set the 
eccentric in correct adjustment to give the right speed. If 
the governor is perfectly isochronous, the new adjustment 
meets the case exactly, and the engine runs at the intended 
speed as before. The load-springs may even be so adjust- 
ed that an increase of load may produce a decrease of 



144 STEAM ENGINES FOR 

speed to any desired extent, or, even more commonly and 
usefully, so that an added load ?nay give increased speed. 
This latter is done in some cases when driving electric 
lights, and also in saw-mills, and for other kinds of variable 
work. In the former case, the engine is adjusted to give 
standard speed when driving full load, and to reduce its 
speed as lights are turned off ; in the latter, the engine 
runs at speed while the saw is cutting, and slows down 
when the work is off. 

The next figure shows the eccentric. A is the main ec- 
centric having an elongated shaft opening ; to this eccen- 
tric is attached the arm B, of which the outer end is pivot- 
ed, allowing the eccentric to swing across the shaft ; this 
motion controls the time during which steam is admitted, 
each stroke. This swinging motion is controlled by the 
rotation of the disc, C, in the following manner : The disc 
has a flange, D, on its side, which is eccentric to the shaft, 
and on the inside of this eccentric flange is a ring, E, which 
engages with a stud, I^, in the main eccentric. Thus the 
rotation of this disc forward and backward causes the ec- 
centric to swing across the shaft. The disc has a sleeve 
encircling the shaft and projecting through the elongated 
shaft opening in the main eccentric, and on the end of the 
sleeve is a flange nut, G, which holds the parts in place. 
The rotation of the disc is produced and controlled by the 
governing forces ; the centrifugal force of the weights met 
. by suitable springs ; and the resistance of the load equilib- 
riated by the centrifugal force of the weights. 

This form of governor is a very safe one, as, should 
breakage of load-springs occur, the engine slows down or 



ELECTRIC LIGHTING PLANTS. 



145 



Stops. The risk of injury of this kind is unimportant, how^ 
ever, if the springs are properly made, as the load carried by 
them is insignificant. A 50 horse-power engine, at 300 revolu- 
tions per minute, carries a load of but about 500 pounds on 
each load-spring. If correctly proportionated and made, 
they should endure indefinitely. The endurance of all 
these springs is the greater for the periods of rest frequent- 
ly given them, and for the fact that they are, much of the 
time, under very uniform tension. 




The Ball Eccentric and Connections. 



The practical result of this novel modification of old 
methods of regulating the engine is that the regulation of 
the steam-engine now can be made to cover more than the 



140 



STEAM ENGINES FOR 



simple preservation of a fixed velocity of rotation. It is 
now possible to determine, within certain limits, not only 
what degree of variation from normal speed shall be per- 
mitted, but also what shall be the normal, and if desired, 
varying, speed of the machine, with varying load. It may 
not only be made to run at a certain fixed speed, but may 
be caused either to increase or diminish the speed, accord- 
ing to a fixed, and economically desirable, law. This new 
principle will probably find many applications, although 
such problems have rarely come to the consideration of the 
designing engineer, hitherto. 

The accompanying peculiar diagrams are taken from the 
recording apparatus of the "Moscrop Indicator," an in- 
strument which automatically and continuously records the 
speed of the engine and its variations. Each revolution 
produces a dot, the height of which above the base-line in- 
dicates the speed. The first of the two diagrams is from an 



AN/ 




MoscROP Speed Diagram. — Fair Regulation. 



engine of 250 horse-power, fitted with an "automatic cut-off," 
and furnishing power to a paper mill. It is claimed to do 
good work ; but the author has no personal knowledge of it 



ELECTRIC LIGHTING PLANTS. 



U7 



The second is furnished, by the owners of the Ball En- 
gine, as illustrating fairly an equally trying case. The 
author has other cards of this kind which, with great varia- 
tion of steam-pressure, nevertheless are very smooth, al- 
though not as smooth as that here reproduced. They are 
also interesting as showing how useful a recording speed- 
indicator may be. Such records are more satisfactory, in 
comparing speeds of engines, than are even the best of 
counters, and vastly more satisfactory than counting by the 
watch, as they exhibit the rate of each revolution, together 
with the variation of rate for extended periods of time. 





































































































































































































































































































































s 


o 


^ 


"* 


SI 


m 


■« 


lO 


o 


nip 


CO 


m 


o 


1-^ 
1-1 


3 


™ 


mil 


s 


m 


,m 


^ 


1- 


§ 


111 


m 


s 


s 


nil 


im 


S 


§5 


mil 


o 


nil 


m 


„" 


iiii 


1,111 


nii 


IIII 


s 


J 






































































































00 






















rx 
























lO 









































































































MoscROP Speed Diagram. — Ball Engine. 

This engine, with its novel governor, is one of the most 
interesting products of mechanical ingenuity that has been 
seen since the days of Watt. It will probably have but 
little influence on the vitally important matter of steam- 
engine efficiency, as that term is customarily applied, that 
is to say, upon the economy of the engine in consumption 
of steam and of fuel ; but it will undoubtedly, in many of 
its applications, be found to have a very important effect. 
Mr. Ball has since the introduction of this device also 
designed other engines of the earlier types. 



148 STEAM ENGINES FOR 

THE IDE ENGINE. 

'' I ^HE engines which have been described are by no 
-^ means the only engines which are deserving of 
mention, and of careful study, as illustrating the peculiari- 
ties of the best modern practice in the field which it has 
been the object of the author to explore. A number of 
other engines, of one or another of the classes which have 
been described and illustrated in the preceding articles, 
have nearly or quite equal claims for consideration. Of 
these engines, only typical or representative examples have 
been sought, and have been selected from the machines 
with which the author is most familiar. One more engine may 
be here described — not as possessing the singular novelties of 
design which distinguish some of those already examined? 
but as affording a good illustration of the principles and 
practice which have come to be recognized as distinctive of 
the latest phase of that progress, which has recently been 
so rapid, in the direction of improved methods of con- 
struction, as well as of design, and in the application of the 
modern materials of construction. The engine is one with 
which the author cannot claim that personal familiarity 
which has led, in some cases, to the selection of those which 
have been previously considered; but a description, such 
as is to be here given, will show that it may fairly be taken 
as a representative of the best practice, in matters of detail, 
which it is the special object of the writer now to exhibit. 

The Ide Engine is of the same class with all the engines 
described in the preceding section — a high-speed engine, 
intended to be driven up to high power and to occupy 
small compass; to regulate with all the accuracy desired in 



ELECTRIC LIGHTING PLANTS. 



I.^Q 



electric lighting, and in the spinning of fine cotton; to have 
good wearing qualities, and to be economical in its use of 
steam and of fuel. The illustrations exhibit its general 
form, and the more important details of the machine. 




Examining it in some detail, it will be observed that the 
frame, although of novel design, is of the same general form 
with those which have been already described in this class, 



I50 



STEAM ENGINES FOR 



possessing that solidity and rigidity that have been seen to 
be an essential feature of all successful high-speed engines. 
The main pillow-blocks are formed in the frame; and the 
cylinder is secured at the opposite end, overhanging as in 




cases already familiar to the reader. The crank-pin is set 
in a disc, which permits counterbalancing, and gives great 
strength. The connecting-rod is tapered from the crank- 



ELECTRIC LIGHTING PLANTS. \ 5 1 

in to the crosshead-end, in the manner now common to 
all fast-running engines. The outlines of all visible parts 
indicate strength and stiffness, and are very neat in design_ 

The valve-gear and governing mechanism are shown best 
by the view of the opposite side of the engine, given in the 
next engraving. The piston-valve is adopted, and is placed 
directly under the steam-cylinder. This arrangement per- 
mits most complete drainage of the cylinder, and thus less- 
ens the danger of accident, should the entrance of water 
with the steam occur to any serious extent. The placing 
of the valve at the side is not an unusual feature of this 
class of engine; but the arrangement here adopted is, in 
this respect, still more advantageous. This arrangement 
also affords a means of getting an equalization of the travel 
of the valve relatively to that of the piston, which is an ad- 
vantage. Still another advantage is that this position of 
the valve-chest gives dry steam from the steam-chest, by 
causing it to act as a trap, as well as drains the cylinder of 
water that may have condensed within it. The connection 
with the steam pipe is made above the line of connection 
between the steam-chest and the cylinder, and it is thus 
rendered possible to remove the former, and get at the 
valve without disturbing the steam pipe. 

The regulation is effected by a governor of the class 
adopted in all engines of this kind, and the regulation and 
the action of the valve are similar in character and in pre- 
cision to those seen in engines already described. The range 
of power, and the distribution of steam at various points of 
cut-off, are shown very beautifully in the indicator diagram 
here given, which was obtained by suddenly throwing off 



T^2 



STEAM ENGINES FOR 



the load; each revolution gives a distinct "card." Steam 
may follow from the beginning nearly to the end of stroke, 
with good exhaust and an excellent range of compression. 
The speed of engine was here 225. The card was taken by 
loading the engine to its maximum power by a Prony 
brake, and then taking the diagrams while the governor 
was adjusting the steam supply, the brake being at the mo- 
ment released. The smallest card is therefore a " friction 
card." The smoothness of action of the regulating mech- 
anism is shown by the uniformity with which the power falls 
off and the cards diminish in area. 




Series of Indicator Diagrams. — Ide Engine. 



The next diagram shows the range of work which such 
engines are capable of doing, and illustrates very finely the 
change in the distribution of steam which takes place in 
this accommodation of the power of the engine to its load. 
It is seen that the compression, as well as the expansion, 
gradually changes in amount as the power varies, both act- 
ing to reduce the area of the diagram with diminishing 



ELECTRIC LIGHTING PLANTS. 153 

power, or to increase it as the required power becomes 
greater. A very interesting effect of this change is to give 
increased economy in the use of steam by checking cylinder 
condensation, the greatest known source of waste of heat, 
just when that loss becomes most serious in both absolute 




Indicator Diagram. ^Ide Engine. 

and relative amount. In some cases, the economy obtain- 
ed, with considerable expansion, by the introduction of 
large compression, has amounted to above 10 per cent. 
Where superheating is adopted, this gain is less; but in the 
usual case, using saturated steam, the use of the valve- 
motion, of which an example is here illustrated, brings with 
it a very important advantage; and nearly all builders of 
such engines are now agreed in testifying to its value. The 
lines of indicator diagrams obtained by the author from this 
engine are unexcelled. The recent types of this engine 
will be described in a later chapter. 

One very important feature of recent progress in the con- 
struction of the steam-engine is well illustrated in the Ide 



154 STEAM ENGINES FOR 

Engine, and affords a special reason for studying it; this 
is the extensive use of steel in its running parts. Within 
a few years it has become possible to obtain from the mak- 
ers of Bessemer and " Open Hearth," as well as of crucible, 
steel, a quality of metal which earlier could not have been 
obtained at all. This is a steel which is distinguished, 
chemically, by its low percentage of carbon and its rela- 
tively high proportion of manganese, and physically, by its 
wonderful combination of ductility and strength. As the 
proportion of carbon decreases in steel it loses strength; 
but it gains ductility and malleability in a far higher ratio, 
and thus it happens that the softer qualities are much bet- 
ter fitted for use in machinery than are the very best of 
wrought irons produced by the ordinary process of pud- 
dling. The former are strong, tough, amply hard for all 
such uses, and perfectly homogeneous; the latter are less 
tenacious, often not as ductile, and are never homogeneous; 
but are full of "cinder streaks," and have a fibrous struct- 
ure that is objeciionable, and is never seen in steels. 
These steels are all made by casting molten metal into in- 
got moulds, and thus securing comparative freedom from 
cinder and defective structure. 

The soft steels are displacing iron in every direction; 
and the probabilities seem to be that in the course of time, 
in the coming "Age of Steel," iron, puddled as is now us- 
ual, will be entirely displaced by these, properly so-called, 
"Ingot Irons." The Ide Engine, as well as other engines 
now coming into market from the shops of the best build- 
ers, illustrate this change of material. It has its piston-rod, 
its connecting-rod, its valve-stems and links, and its smaller 



ELECTRIC LIGHTING PLANTS. 



^55 



journals, all of steel. Large castings are not usually made 
in steel in this country, but all small parts are coming to be 
made in that remarkable metal. 



ENGINES OF THE NEW YORK SAFETY STEAM-POWER CO. 

In the course of the somewhat extended series of descrip- 
tions of standard forms of engine which is now soon to be 
closed, it will have been observed that the tendency has 
been toward the reduction in number of parts, and increas- 
ing simplicity of mechanism as the speed of engine is in- 
creased. The earlier types of engine having detachable 
cut-off apparatus as a part of the valve-motion were engines 
of moderate speed of piston and of comparatively long 
stroke, and, therefore, of even more moderate speed of ro- 
tation. The latter forms of standard engine are of simpler 
construction, and of higher speed of piston, and of much 
higher speed of rotation. This difference is not only due 
to the necessity of reducing the number of parts and secur- 
ing greater positiveness of action in the valve-gear, but it is 
also due to the more general recognition of the fact that 
economy of steam and fuel consumption is but one of the 
economies to be studied in the use of steam as a motive 
power, and that the cost of securing great economy of steam 
and fuel may be such as to more than compensate the sav- 
ing effected by such expenditure. This is especially true of 
small powers, and common experience has shown that it is 
seldom advisable to construct complicated valve-gears for 
such engines, as the cost rarely comes within the commer- 
cially economical limit. This principle has probably been 
carried too far; and the author has no doubt that engines of 



I 56 STEAM ENGINES FOR 

the higher grade may be often found commercially econom- 
ical for even very small powers. The field for the simpler 
class of small engine, nevertheless, is enormously extensive; 
and the number annually built is very great. 

But little attention, comparatively, has been paid to the 
design and construction of small steam-engines until very 
recently. The engineer has been too often inclined to look 
upon this as too small a matter to demand the thought and 
the time that he has freely given to larger and more at- 
tractive work. It is now different, and some excellent 
forms of small engines are to be found in the market. It 
is the intention of the author here to describe a single ex- 
ample of this class of machine, not as the only good engine 
of the class, but as a type of this class. 

The British builders of portable and agricultural engines 
were the first to develop the art of steam-engine design and 
construction in this department. A dozen years ago, they 
were building engines of as little as 20, or even 10, horse- 
power, which demanded but 3 pounds, and even less, of 
coal pel horse-power per hour. As early as 1867, they 
reached the figure 4.13 pounds;* in 1S70, it became 3.73, 
and, in 1872, the Reading Iron Works built an engine of 20 
horse-power which, on trial at Cardiff, required but 2^ 
pounds of picked coal per hour and per horse-power. This 
engine had a cut-off valve on the back of the main valve. f 
Single valve engines have never done as well; but some of 
them have nearly approached these figures. A consump- 
tion of 5 pounds of coal per hour and per horse-power is a 

1 . Mechanical Engineering- at Vienna ; Reports on the Vienna Exhibition : R. 

H. Thurston. Washington, 1878. 

2. Manual of the Steam Engine, Vol. I. § 38. 



ELECTRIC LIGHTING PLANTS. 15;? 

good figure, and is rarely attained in such small engines. 
The best of them may be expected to use from 5 to 7 
pounds and to consume, therefore, from 40 to 60 pounds of 
steam, averaging perhaps about 50, on the basis of the in- 
dicated power. 

Among the earliest of American engineers to turn atten- 
tion to this department of mechanical engineering, were 
Messrs. Babcock & Wilcox, v/ho have become well known 
as the inventors of a successful form of "sectional" steam 
boiler. The style of engine which was designed and intro- 
duced by them, and built by the New York Safety Steam 
Power Co., has now become as generally accepted as stand- 
ard among builders of small engines as has the Corliss en- 
gine among constructors of drop cut-off engines. It has 
been copied in all parts of Europe, as well as in the United 
States. This may be taken as representative of the best 
methods of construction in this country, and as exhibiting 
the elegance in proportions, and that excellence of material 
and workmanship, which are now becoming recognized as 
desirable in steam-engines of even the smallest size. In 
fact, as has been seen, the opportunity here offered for im- 
provement, and for economizing steam and fuel consump- 
tion, is much greater than with large engines; and these 
excellencies are, therefore, the more desirable. 

The engraving exhibits the form of the engine here to be 
described. It is a " vertical engine " mounted upon a base- 
plate of neat and strong form, and with the steam-cylinder 
bolted by the lower head to a very strong and very graceful 
frame. The main journals are carried in bearing construct- 
ed in the frame, and consequently free from liability to loss 



STEAM ENGINES FOR 



of perfect alignment, or to unequal wear. The valve is 
either a plain, locomotive-slide, or, preferably, a piston valve. 
The latter is fitted in a detachable seat, which can be 
easily removed for renewal of seat and valve, should acci- 
dent or wear ever make it necessary. 




N. Y. Safety Steam Power Co.'s Engine. — 5 h. p, 

The vertical position of the engine prevents wear within 
the cylinder becoming serious or un symmetrical. The 
pistons are hollow, and are packed with rings set with suf- 



ELECTRIC LIGHTING PLANTS. 



^59 



ficient spring to keep them up to a bearing. The cross- 
head, which is shown in the following engraving, has its 
gibs turned to fit the guides in the frame, which latter are 
part of the casting of the frame and are bored out in line 
with the cylinder, and cannot possibly get out of line. 

K 





Crosshead. 

Crosshead. ' 

The engine above illustrated is of small size — 4 or 5 
horse-power — and has been especially designed for electric 
lighting purposes. The governor is that known as the 
"Waters Governor ;" it regulates by adjusting the supply of 
steam passing to the engine through a throttle valve — a 
method which seems to have been here more successful 
than is usual in engines having to perform so exacting a 
kind of work. The speed of this engine is usually about 
250 revolutions per minute. 

Larger engines of this style are often constructed ranging 
up to 100 horse-power. The heavy engines, when of 15 to 
100 horse-power, are given an independent crank-shaft 
pillow-block and a counterbalanced disc-crank. In these 
engines, of all sizes, the modern innovation of the use of 
steel for running parts is very generally introduced. The 
rods, pins, and minor parts are of this metal; the bearings 



I Co 



STEAM ENGINES FOR 



are usually of bronze lined with Babbitt metal, and are 
given large area. Crank-shafts are either of steel or of 




lo H. P. Vertical Engine. -N. Y. S. S. P. Co. 
hammered iron. As is customary with all well con- 
structed engines, these engines are set up and operated in 
the shop long enough to exhibit all defects and to afford 



ELECTRIC LIGHTING PLANTS. 



l6i 



opportunity to make all adjustments before sending them 
out, and are thus made safe against those annoying delays 
which otherwise attend the introduction of such machines. 
The parts are made to gauge, and therefore interchangeable; 
and it is thus made easy to replace them when worn or in- 
jured, at minimum expense and with little delay The 




Semi-Portable Engine, 



valves, and their seats, even, when worn, are taken out, sent 
to the shop, and the spare valve and seat, already fitted, 
takes the place of the parts removed. 



1 6 2 STEAM ENGINES FOR 

Where engines are of large size, they usually have the 
engine room and boiler room distinct; with these small 
engines, however, it is found often to be desirable to place 
engine and boiler side by side, and even upon a common 
base, as is illustrated by the last of the preceding engravings. 
This forms what is known, frequently, as the " semi- 
portable " engine, to distinguish it from the "portable," 
which last named style is mounted on wheels. 



THE ERICSSON AND WESTINGHOUSE ENGINES. 

A LL of the engines which have been considered in the 
■^-^ preceding articles are of one general type — that 
known as the " double-acting reciprocating engine." Before 
the time of James Watt, the only engine in extended use, 
even in the limited field in which the steam engine was then 
employed — that of pumping water from mines — was a "sin- 
gle-acting" engine — the Newcomen engine, which had then 
almost entirely superseded the so-called engine of Savery. 
Watt invented, first, the separate condenser, and then the 
double-acting engine, thus increasing the power of the ma- 
chine and rendering it, at last, applicable to the turning of 
a crank and the driving of machinery and mill-work. In 
the " single-acting engine," the steam drives the piston in 
but one direction, and the return stroke must be made 
without the production of useful work. In the " double- 
acting engine," the steam acts upon the piston in both di- 
rections, and with practically equal effect. Thus, a more 
regular action is secured with a given weight of balance 



ELECTRIC LIGHTING PLANTS. 16: 

wheel, or the same regularity with a wheel of one-half the 
weight of that required for the older form of engine. This 
smoothness of motion is, in such work as is here considered, 
one of the most essential features of the best steam engine 
economy. At the speeds which have been now attained, 
however, the inertia of moving parts becomes so great that 
moderate variations in the impelling power become com- 
paratively insignificant, and have no perceivable effect upon 
the smoothness of revolution of the crank-shaft. 

The double-acting engine evidently possessed greater 
power than its predecessor, when of the same size, and the 
'' efficiency of the machine " was correspondingly increased. 

The very conditions which have been thus made to aid 
in securing regularity have, however, introduced a new dif- 
ficulty: At every revolution of the engine, the crank 
*' turns the centre" twice; and, at every passage of the 
centre, the direction of pressure upon the crank-pin is re- 
versed, thus producing a shock which is proportional to the 
difference of pressure, the suddenness with which it is felt 
at the pin, and the extent of the "lost motion" between 
the pin and its bearings. Some lost motion must always be 
permitted here, to avoid danger of heating of the journal 
and injury to the machine. The counteracting adjustments 
are found to be, usually, the utilization of the inertia of the 
reciprocating parts, as in the Porter- Allen engine; the 
adoption of heavy compression, as in the several engines 
afterward described, and very careful adjustment of the fit 
of the brasses on the pin. With the skilful use of these 
expedients, and with the introduction of a perfection of 
workmanship, and of such qualities of material, as have 



164 STEAM ENGINES FOR 

never before been seen, the " high-speed engine " has been 
made successful at as high as 400, and even, in some cases. 
600 revolutions per minute. The lower of these figures may 
be taken as that representing the maximum in standard, and 
usually best, practice. 

But much higher speeds than these are sometimes de- 
manded; and engines must, in the future, be built to run, 
regularly, steadily, and safely, at, probably, very much 
higher velocities. This may, ultimately, lead to radical 
changes in the design of the now standard forms of fast en- 
gines. Nevertheless, the limit of speed has by no means 
been reached, even at the higher of the above speeds, with 
the common type of engine. The speed of even 450 times 
the cube root of the length of stroke, now a common figure, 
and three times that given by James Watt's rule, is occa- 
sionally greatly exceeded. Captain Ericsson designed an 
engine, now many years ago, for the electric lighting ap- 
paratus of the Delamater Iron Works, which was then 
kept running, every evening for two or three years, at 1,250 
revolutions per minute, without giving the slightest trouble, 
or meeting with the most insignificant accident. The pis- 
ton speed is about twice that of the average " high-speed " 
engine, and six times that adopted by Watt. It is probably 
the highest speed ever attained by a reciprocating engine. 
This engine is preserved at Sibley College. 

The object of the inventor was to design a steam-engine 
for the special work of driving small dynamo-electric ma- 
chines, and hence to secure great stability and strength, a 
minimum number of parts requiring lubrication, and abso- 



ELECTRIC LIGHTING PLANTS. 



165 



lute certainty that the parts retained should be, at all times, 
thoroughly supplied with the lubricant. The engine is 
therefore made a " half trunk " engine, the trunk, F, F, 
serving as an oil reservoir. The joint in the eccentric rod 
is provided with a piston moving in a cylindrical guide, 
JV, which is also an oil reservoir. The cylinder, C, and 
base-plate, JB, are in one casting, upon which is set the 




The Ericsson Engine. 
hollow frame supporting the crank-shaft, JI, E, and balance 
wheel. Every journal and rubbing part has an oil reser- 
voir and special provision for effective lubrication. The 
whole engine is a model of the product of that most efficient 
kind of ingenuity which seeks definite ends by the most 



l66 STEAM ENGINES FOR 

simple and direct means. This " plant," engine, dynamo, 
and lamps, is now preserved in Sibley College. 

The limits to velocity of piston and speed of rotation 
have, from the beginning of steam engine practice, been 
thus gradually set farther and farther back; and one 
after another of the limiting conditions have been suc- 
cessfully met and overcome. The earliest limit was that 
found in the bad workmanship and material which Watt 
and his contemporaries encountered, and which gave rise 
to heated journals at even what would now be considered 
very low speeds, and at very small powers. This defect 
being gradually overcome, the next, and a comparatively 
modern, difficulty was found in wear, and the "pound," 
which took place when the lost motion of journals in the 
line of the connecting rod was taken up, at the passing 
of the centres. This difficulty was met in two ways, as 
already repeatedly stated — by making use of the inertia 
of the reciprocating parts, as was done by Porter and 
Allen, and by heavy compression as is practiced in nearly, 
or quite, all of the high speed engines of to-day. The 
first method can be adopted only when careful propor- 
tioning, after calculation, of the weights and velocities of 
the moving parts, has determined the proper weights of the 
compensating pieces. The latter adjustment may be made 
either by calculation or by experimentally finding the com- 
pression giving smoothest running. This effect of increas- 
ing compression can be most satisfactorily seen in the ma- 
rine engine, in which, whatever the speed of the machine, 
and whatever the steam pressure, or however loose the 
journal, the link may be raised so as to gradually check the 



ELECTRIC LIGHTING PLANTS. 



167 



pounding at the centres, and finally to eliminate it altogether, 
the engine often being thus brought to work silently and 
smoothly at speeds far above those which, without compres- 
sion, would be very troublesome, if not absolutely danger- 
ous. This is an experiment which the writer has repeated 
on many engines, and almost invariably with the same satis- 
factory result. 

Some lost motion must always be permitted at the crank- 
pin, and these expedients are usually found to meet the case. 
They probably have their limits, however. There comes a 
time, as speeds are increased, when the weight of running 
parts, as calculated for strength only, becomes as great as is 
desirable to effect the compensation by their inertia ; there 
comes a time, as compression is increased, when the "cush- 
ioned" steam is carried up to boiler pressure, and this would 
seem the natural limit in this matter. The next device, 
chronologically, adopted by the engineer, is that of prevent- 
ing the lift of the brass of the crank-pin and of the cross- 
head pin at the turning of the centres, while still leaving the 
freedom of fit required to give safety from heating. This 
last expedient is that which has led to the construction of a 
class of engines which are as peculiar and as typical as either 
of the classes which have been already described. 

THE WESTINGHOUSE ENGINE 

belongs to this new class, and is here taken as its represen- 
tative. The change of construction characteristic of this 
type of engine is a return to the original " single-acting" 
plan of engine. This has been often proposed, and not in- 
frequently attempted ; but the success attained has not, as 
a rule, been satisfactory. Two, and three, and four, cylin- 



i68 



STEAM ENGINES FOR 



ders have been tried, in the endeavor to secure regular mo- 
tion while taking steam only on one side of the piston ; very 




The Westinghousk Compound Engine. 

high speeds of revolution have been attained ; but the cost 
of steam has been found too great, and their use has not 
become general. The Westinghouse engine has proved it- 




Section of Compound Engine. 



(^^E-^> 



p..f^}M Wtf.> 



""linJiliiiH, ,l«i«i\ i'^ '« 1 1 "««ii 
mjiii I Ipll' ' 




\ 1^-11— %"''B.^^fe\ 




The "Standard" Engine.— Working Parts. 



ELECTRIC LIGHTING PLANTS. 169 

self to possess the elements of commercial success, and is, 
therefore, to be taken as illustrating what can be done in 
this direction, by good designing and good business man- 
agement. 

It is evident that, if steam pressure comes upon but one 
side of the piston, the engine can pass its centre without 
the brass lifting clear of the pin, and thus may be driven 
up to any speed without liability of injurious pounding. 
For high speeds, as the engineer of to-day looks upon 
them, this is evidently the type of engine to be looked to 
for smooth and successful working. The illustrations show 
how, in the Westinghouse engine, this end is reached. 
The engine has two cylinders fitted with single-acting pis- 
tons forming trunks filling the bore of the cylinder, giving 
a long steam-tight bearing, and taking the connecting-rod 
pin at a point at which no tendency to rock the piston 
can be produced. The top of the piston is cored out to 
prevent transfer of heat from the working to the non- 
working end. The rods take hold of the crank-pins 
within an enclosed chamber forming part of the engine 
frame. This frame and bed-plate also acts as a reser- 
voir for oil lubricating the journals and pistons, which 
oil floats on water and is dashed up over the moving 
parts so enclosed, at every revolution of the engine. 
No other attention is required than to keep a supply 
of oil in the chamber, by filling as loss occurs by leak- 
age. In fact, the whole engine is thus shut in by its 
frame, and its working parts are invisible, while working 
— an arrangement at once a means of security and con- 
venience. 

The valve adopted in the Westinghouse engine is a piston 



170 



STEAM ENGINES FOR 



valve of the class already described, but having some pecu- 
liarities specially adapting it to its use in this engine. 

A single piston-valve distributes steam to both cylinders, 
securing, at the same time, some special advantages, and 
illustrating ingenious adaptations to this singular and in- 
genious type of engine. The accompanying engravings 
exhibit the forms of the three designs of this machine in 
common use: the "Standard," the "Junior," and the 
Compound. In the first, the valve is placed in the verti- 
cal plane ; in the others it lies along the top of the two cyl- 
inders. The essential features of the three engines are very 
similar, and equally characteristic. To insure freedom 
from danger from water entering the cylinders, the great 
source of risk with high-speed engines, relief valves are 
fitted to all, and are illustrated, in the perspective drawing, 
at either end of the valve chest. It is still better shown in 
the accompanying sketch of the valve chest employed in the 
compound engine, which also exhibits the internal construc- 




Valve Chest. 



ifimfllilBi 




The "Junior" Engii«e. 




The Westinghouse Engine. — Section Through Shaft. 



ELECTRIC LIGHTING PLANTS. 



171 



tion of the chest and the location of ports, by-pass, and 
fittings. 

The main valve, thus fitted, is easy of access and of 
removal or replacement ; the crank-case shuts in the lubri- 
cating fluid, a mixture of oil and water, and allows the 
splashing action of the cranks to insure thorough and unin- 
termitted lubrication, with flooded journals ; and, at the 
same time, the accident of piston leakage, should it occur, 
is immediately revealed by the exit of steam from the vapor 
pipe. Leakage at the valve is detected by removing the 
valve-chest bonnet cover, and working the engine in that 
condition. Access to the crank-case is obtained by remov- 
ing the bonnets seen in the perspective drawing 
of the engine. Since this engine is especially 
designed for high speeds of rotation, the ne- 
cessity for insuring permanence of action and 
durability by positively certain lubrication is 
vital. The construction of the connecting 
rod, as seen in the next figure, illustrates one 
of the adaptations of details of construction 
to this exigency. 

The rod consists of a body and two boxes, 
with a take-up wedge between the body and 
the top of the l6wer box. Both the upper 
and lower boxes are in halves, made of hard 
brass, babbitted. A continuous strap has its 
ends bolted to the lower half-box and runs 
around the upper, binding the whole together. 
Tightening up on the wedge-bolt will expand the rod 
lengthwise, and take up both ends alike, and to any 




Connecting 
Rod. 



172 



STEAM ENGINES FOR 



desired adjustment. The strap transmits no strains. This^ 
as many other parts of these machines, has been designed 
with a view to securing safety in continuous rapid working, 
while retaining low cost of construction in manufacturing in 
quantities. The makers report one case in which one of 
these engines, of ten horse power, was in continuous oper- 
ation thirteen months and eight days, at a speed of 500 
revolutions per minute. Such speeds as these are found 
useful in securing direct connection and its attendant 
advantages, in driving electric light and power machinery ; 
and the makers of these, like those of a number of other 
engines of the older type, are making this application with 
success. In some locations, as on shipboard, this arrange- 
ment is almost obligatory ; where practicable, it is probably 
usually desirable. 

The governor of these engines, shown well in the last of 
the sketches of the machine, is similar in principle to those 
already illustrated in the previously given accounts of the 
high-speed engines of other forms. It is a " shaft govern- 
or," directly acting upon the valve stem and determining 
the momentary range of expansion. It illustrates more 
clearly than do the engravings already given, however, the 
following principle, which may often be utilized in a prop- 
erly designed governor of this class : It will be observed 
that the balls are here weights of elongated form, reaching 
across the line of the shaft, and so set that any sudden 
jump of the engine, whether in acceleration or in retarda- 
tion of its speed, will tend to carry the shaft past its mo- 
mentary relation of angular position relatively to the balls, 
and thus to, in the one case, increase the ratio of expan- 



ELECTRIC LIGHTING PLANTS. 173 

sion, and, in the other, throw the valve into a position 
for "following further," supplying more steam and doing 
more work ; Avhile the instantaneous action thus secured 
insures as instantaneous adjustment of the steam-supply to 
the load, irrespective of the action of the centrifugal force 
of the balls. The most perfect governors of this type have 
been known to hold the speed constant, within a fraction of 
one per cent., not only as an average, but even preventing 
that jerk and oscillation, when, as by breaking the circuit of 
an electric lighting system, or restoring contact, the load is 
instantly completely thrown on or off, which is commonly 
both noticeable and objectionable with less efficient govern- 
ors. This action of the "inertia governor" is peculiarly 
valuable in such work. It is obtained, in this case, by 
making the paths of the center of gravity of the governor 
balls traverse the radial line between the center of suspen- 
sion of the arm and the shaft-center, as nearly as possible 
at right angles, and as near the pivot as practicable. Ex- 
perience shows that, in a successful governor of this kind, it 
is possible to make the fluctuations of speeds entirely insen- 
sible, whatever the extent or rapidity of the changes of 
load. The centrifugal element maintains the mean speed 
of successive strokes with precision, and the inertia element 
insures it against sudden surges. 

The cranks of these engines are set opposite each other, 
and thus a balance of reciprocating parts is secured which 
gives freedom from jar and from inconvenient or dangerous 
shaking of the engine and its foundations. The ingenious 
and novel methods of securing certainty of lubrication ; 
the constant direction of forces tending to produce heavy 



174 



STEAM ENGINES FOR 



Strains ; the small number of parts ; the reduced labor of 
attendance ; the compactness, solidity, steadiness, safety at 
maximum speeds, and general effectiveness are such as to 
make it one of the most interesting of all the modern forms 
of steam-engine. 

The forms of simple engine illustrated in the described 
figure and the last engraving of this series, by a natural 
process of evolution, developed into the compound- engine 
shown in the first two engravings ; the one cylinder being 
made properly proportioned to the other, and the steam dis- 




Westinghouse Compound Engine Diagram. 



tribution being effected by the same valve, as shown ; the 
steam rejected from the smaller engine being passed into 
the larger, and thence into the condenser or into the atmos- 
phere. The principles of the compound engine will be dis- 
cussed in the next chapter ; but a peculiarity of this type 
may be best described here. The indicator diagram pro- 
duced by the engine is very nearly that shown in the 
accompanying figure. By giving the intermediate chamber 
or receiver, which here becomes a clearance space for the 



ELECTRIC LIGHTING PLANTS. 



175 



small cylinder, a volume having the same proportion to the 
small cylinder that the volume of the latter bears to the 
large cylinder, with several ingenious and effective correc- 
tions for minor variations of kinematic and thermal move- 
ment, the single valve is made to give precisely the distribu- 
tion desired : such that the expansion in the small cylinder 
from any point. A, and into the larger, up to the cut-off of 
the latter, will always give a terminal, at B, such that the 
compression in the small cylinder will carry the line up to 
boiler pressure. The action of the low pressure compres- 




^^_ £^^aHoun d_non-conapn«ino 



^S LPpund condpusinQ. ___ 

-S i; vs; 



^1 



Economy under Varying Loads. 

sion completes the diagram in singularly admirable form, 
and, incidentally, aids by reducing the liability to wastes by 
internal condensation. The curious result is thus reached 
that the total range of temperatures and pressures and their 
division between the two cylinders remain nearly constant, 
whatever the load on the engine ; and the machine is thus 



176 



STEAM ENGINES FOR 



caused to adapt itself comparatively perfectly to all loads, 
and to vary comparatively little in its efficiency, and this 
with a single valve and the simplest of mechanism. This 
result is illustrated by the accompanying diagram, which 
the makers give as the result of their experience with the 
variations of economy of the three classes of engine with 
varying loads and correspondingly varying expansions, and 
by the following figures : 

WATER RATES, BY TEST, UNDER VARYING LOADS, 



Horse-Power. 


3IO 


170 


140 


115 


100 


80 


50 


Non-condensing . . 
Condensing 


22.6 
18.4 


21.9 
18. 1 


22.2 
18.2 


22.2 

18.2 


22.4 
18.3 


24.6 
18.3 


28.8 
20.4 



ELECTRIC LIGHTING PLANTS. 177 

VI. 
Multiple-cylinder Engines ; Proportions of Parts. 

E have now made a tolerably complete survey of the 



w 



whole modern field of steam engineering as far as 
it is covered by our earlier practice, and have seen a very 
steady progress from the best types of a generation ago to 
the most representative examples of the later simple 
forms It is seen that the direction of change is still that 
which, as has been often pointed out by the author, has 
been observed from the days of James Watt. The principal 
points found worthy of notice have been the increase in 
economy and general efficiency by a tentative and empirical, 
but none the less steady and uninterrupted, method of ad- 
vance. The pressures of steam have been slowly, but con- 
stantly, rising; speeds of piston, and of rotation, have been 
as constantly increasing; the effectiveness of the governor 
\ias been made greater and greater; the ratio of expansion 
at maximum efficiency has been very slowly increased, by 
the gradual reduction of "cylinder-condensation;" commer- 
cial considerations have been brought definitely into view; 
the efficiency of engine has been improved by reduction of 
size, weight, and friction of engine; and thus we have been 
able to see a gradual change of type of engine effected, the 
engineer modifying his designs to meet the demands of the 
time, until we have insensibly, and almost without suspect- 
ing that progress has been going on, passed across a new 
line and entered upon an epoch, in steam-engine construc- 
tion, as marked in its period and as well defined, as to its 



178 STEAM ENGINES FOR 

beginning, as was that which, at the middle of the century, 
was distinguished by the introduction of the inventions of 
Sickles, Corliss, and Greene. 

The latest phase of this progress is to-day witnessed in 
the rapid introduction of the multiple engine in all de- 
partments of electric work. There has been made, recently, 
a more careful study of the relative merits of the older 
"drop cut-off" engines and the modern "high-speed" 
type. This has led to the careful discrimination of the 
conditions under which each form of engine is advisable. 
The former, as constructed by the best makers, commonly 
excels in economy; the latter excels in compactness, cheap- 
ness, and in nicety of regulation. Where large power of 
uniform amount is demanded for considerable periods, 
without fluctuation or intermission, the older type is often 
the better; but, when the work is variable in amount, called 
for in irregular and uncertain periods, and capable at the 
same time of being divided among several engines, the later 
type is very generally advised. Thus it happens that both 
types of engine find constant employment and an increasing 
market. 

The most striking feature of current change is the intro- 
duction of the multiple engine, and in both of these two 
principal classes of engine. A very large number of these 
engines with detachable valve-gear may now be seen at 
work where large " plants " are in operation, and nearly 
every builder of the "high-speed automatic" engine is now 
" compounding " or preparing to compound his machine. 
The method and the serious importance of the wastes oc- 
curring in all heat-engines, in consequence of the impracti- 



' ELECTRIC LIGHTING PLANTS. 1 79 

cability of constructing their working cylinders of a non- 
conducting substance, have already been stated.' 

The unavoidable thermodynamic waste is rarely less than 
seventy-five or eighty per cent., and the internal wastes by 
conduction and storage, with subsequent rejection, by cyl- 
inder or internal condensation, as it is customarily called, 
and by leakage, range from ten per cent., as a minimum, 
perhaps, to twenty-five or thirty per cent., in good engines; 
to fifty per cent, in many cases, and even to much more 
than the latter proportion in exceptional cases. It is this 
which constitutes, ordinarily, the great source of loss and 
inefficiency of the real, as distinguished from the ideal, 
engine. 

The amelioration of wastes thus becomes an impor- 
tant matter.- The three methods which have been found 
advantageous, and, in special cases, fairly effective, are: 

(i.) Superheating ; 

(2.) Steam jacketing ; 

(3.) " Compounding." 

It is evident that, if the steam can be introduced into the 
engine at such a temperature that the cooling action of the 
metal of the cylinder will not cause its condensation initially, 
and the stroke may be performed without condensation in 
consequence of doing work, no loss of heat from the cylin- 
der can take place by re-evaporation; and if no such loss 
occurs, the waste of heat at entrance, in turn, by initial 
cooling, will be reduced. Superheated steam, also, is a 

!• Chapter H., p. 9. 

2. This portion of this chapter is mainly condensed from a paper by the 
author, read before the American Society of Mechanical Engineers, November, 
1889. 



i8o STEAM ENGINES FOR 

non-conductor and a non-absorbent of heat, precisely like 
the permanent gases. It is thus, also, less liable to this 
waste. But it is found in practice that superheating be- 
yond a very moderate degree, perhaps looto 150 degrees 
Fahrenheit, is inadvisable on account of risks of injury to 
engines and cost of repairs to superheater, which more than 
compensate its advantages. 

Steam-jacketing is another and a common partial remedy 
for this waste. By surrounding the steam-cylinder with the 
steam-jacket, it is possible to produce, in part, the effect of 
superheating; that is, to secure dryer steam in the engine 
throughout the stroke. The amount of re-evaporation, dur- 
ing the period succeeding cut-off and up to the closure of 
the exhaust-valve, and the quantity of heat of which the 
cylinder is thus robbed, measures the amount of initial con- 
densation and waste, and the weight of steam which must be 
supplied in excess of the thermodynamic demand to com- 
pensate that loss. The effect of the addition of a steam- 
jacket depends upon the conditions of operation of the 
engines, largely, and may be productive of marked advan- 
tage, or, under unfavorable conditions, of no important use- 
ful effect. High-speed engines derive less advantage from 
its application than slow-moving machines; and compound, 
or multi-cylinder, engines are less dependent upon it for 
economy than are simple engines. The addition of this 
expedient, if properly performed, appreciably increases the 
magnitude of the ratio of expansion at maximum efficiency 
of fluid. The assumption is commonly made that the 
superheating is retained throughout the stroke, and that 
steam- jacketing may be relied upon to keep the working 



ELECTRIC LIGHTING PLANTS. 



charge dry and saturated throughout the stroke; but neither 
of these hypotheses, as employed in the theory of the engine, 
is probably, as a rule, practically correct. 

^'Compounding,''' ox the use of the multiple-cylinder engine, 
in which the steam exhausted from one cylinder is again 
worked in a succeeding one, is the most familiar of devices 
for extending the economical range of expansion and in- 
creasing the efficiency of the engine. The limit to the 
useful extension of the expansion of steam in a single cylin- 
der is found to be determined by the magnitude of the 
wastes incurred in the operation of an engine of which 
the working cylinder is a good conducting material. Any 
method of reducing this waste of heat internally will enable 
the efficiency of the engine to be increased by further 
profitable extension of the ratio of expansion. Common 
experience with the best constructions, and considerations 
which need not be here reviewed, show that the engineer 
may reasonably expect, by good design, construction, and 
management, to secure an economy of steam which is fairly 
measured by the following table, the ratios of expansion, r, 
taken being, for each case, those which give best results for 
a given engine, engines of fair size being taken : ^ 

Steam per Horse-power per Hour, 
At best ratios of expansion in best engines. 

r 3 4 5 6 7 8 lo 12 15 20 25 50 75 
lbs. 32 27 25 22 20 20 19 17 16 14 14 II 9 

kgs. 15 12 II II 9 9 9 8 6 6 6 5 4 

I. Several Efficiencies of the Steam Engine; Trans. A. S. M. E., and Jour. 
Franklin Inst., 1882. 



t82 STEAM ENGINES FOR 

and ten per cent, better figures than these have been actu- 
ally reported in peculiarly favorable cases. 

Assuming it to be possible to divide the waste by cylinder 
condensation and leakage by two or more, it is evident that 
the limit to economical expansion and transformation of 
heat into work will be set correspondingly further away. 
This is precisely what is done by the multi-cylinder engine. 
The internal wastes are reduced approximately to those of 
the most wasteful single cylinder, and the gross percentage 
of waste is made less in the proportion of this division. 
The heat and steam rejected as waste by internal transfer 
without transformation from the first cylinder, is utilized in 
the second nearly as effectively as if it were received directly 
from a boiler at the pressure of rejection from the first cyl- 
inder. Insomuch, therefore, as the pressure can be in- 
creased and the increase utilized by the addition of another 
cylinder, gain is secured. 

The practical questions thus meet the engineer : To 
what extent can this principle be availed of ? what range 
of pressure and what ratio of expansion should be assigned 
to a single cylinder ? and how many cylinders should be 
adopted to give best results with the highest steam pres- 
sure practicable for a specified case ? Common experience 
aids in solving this problem by showing that the very best 
results are ordinarily obtained, in each class of multi- 
cylinder engine, when, the engine being properly designed 
for its work, terminal pressure for the system can be eco- 
nomically made something above the sum of back pressure 
in the low-pressure cylinder, plus friction of engine. This 
total may be usually taken as a maximum, probably, at 



ELECTRIC LIGHT! AG PLANTS. 1 83 



about eight or ten pounds above a vacuum. The latter 
figure will be here assumed. 

The Fundamental Principles are now easily per- 
ceived. There are three main facts upon which to base 
our theory of the multi-cylinder engine. These are : 

(i.) Economical expansion in a single cylinder' has a lunit, 
due to increasing internal wastes^ which is found at a com- 
paratively low ratio of expansion. 

(2.) The method of expansion jnay be, for practical pur- 
poses such as are here in view, taken to be approximately 
hyperbolic j the terminal pressure being somethittg above that 
which corresponds to the sum of all useless resista?ices, and 
which may be here taken, as, for example, about ten pounds 
per square inch above a vacuum. The division of the initial 
pressure by this tertninal pressure will thus give an approxi- 
mate measure of the desirable j'atio of total expansion for 
the best existing eftgines. 

(3.) All steam entering any one cylinder will be rejected, as 
steam/ ijito the succeeding cylinder, external wastes being 
neglected, and into the condenser j and the full amount of 
steam condejised at entrance by absorption of heat by the in- 
terior surfaces of the cylinder will be re-evaporated later, 
and will pass into the condenser or into the next cylinder j 
and heat transferred in the one direction, in the one process, 
will be transferred in precisely equal amount in the opposite 
direction in the other. 

This last point is a very important one, and is very easily 
established. The cylinder, when in steady operation, is 

I. This the author would denominate Hirn's principle. See a paper by M. 
Dwelshauvers-D^ry in the Bulletin de la Societe Industrielle de Mulkouse, Octo- 
ber, 1888, on the theory of single-cylinder engine. 



STEAM ENGINES FOR 



neither permanently heated nor permanently cooled ; no 
progressive heating can go on, as it would, in that case, 
become heated above the temperature of the steam and 
become a superheater ; no progressive cooling can occur, 
since, in that case, the cylinder would become a condenser 
of indefinite capacit)r. It must, therefore, transfer to the 
next element of the system all the heat which it receives, 
assuming that external radiation and conduction may be 
neglected, and that the Rankine and Clausius phenomenon 
of internal condensation, by transformation of heat into 
work, is ignored. It also further follows that the introduc- 
tion of one or of many cylinders between the terminal ele- 
ment and the boiler does not, through cylinder-condensation 
alone, affect the operation of the latter cylinder, however 
great that condensation may be ; provided the operation of 
the added elements is effected by raising the steam pressure 
commensurately, leaving the final element of the series the 
same initial pressure as before. The total waste by this 
form of loss is thus evidently measured, in the case of the 
multi-cylinder engine, by the maximum waste in any one 
cylinder. If all are equally subject to this loss, the rejected 
steam of re-evaporation from any one cylinder, as the high- 
pressure cylinder, supplies precisely what is needed to meet 
the waste by initial condensation in the next ; and so on 
through the series. Thus the use of a series of cylinders, 
in this manner, divides the total waste for a single cylinder, 
approximately, at least, by the number of cylinders ; and it 
is in this manner that the compound system gives its remark- 
able increase of efficiency. As stated by the author, many 
years ago, " The serious losses arising from condensation 



ELECTRIC LIGHTING PLANTS. 185 

and re-evaporation within the cyHnder, and which place an 
early limit to the benefit derivable from expansion, affect 
both types of engine, and so far as seems now known, 
equally;"' but the compound type permits the intercep- 
tion of the heat wasted from one cylinder, for utilization by 
its successor, in such manner that the total waste becomes, 
practically, that of the low-pressure cylinder alone. If any 
one cylinder wastes more than another, the total waste is, 
as above stated, measured more nearly by the loss in the 
most wasteful member of the system. 

Thus the three principles which have been above enun- 
ciated give a means of constructing a philosophy of the multi- 
cylinder engine, which will meet the essential needs of the 
designer and of the student of its theory. The first principle 
shows that, a limit existing to economical expansion in a 
single cylinder, the advisable number of cylinders in series 
may probably be determined, when that limit is ascertained, 
either by experiment, by general experience, or by rational 
theory and computation. The second principle shows that 
we may find a tentative measure, at least, of the desirable total 
ratio of expansion for maximum efficiency, when the best 
terminal pressure for the chosen type of engine is settled 
upon. This total range is divided by the admissible range 
for a single cylinder ; or, perhaps better stated, the total 
ratio is a quantity which should approximately equal the 
admissible ratio for a single cylinder, raised to a power de- 
noted by the number of cylinders. Combining thus the 
two considerations referred to, we obtain a determination, 
probably fairly approximate, of the proper number of cylin- 

I. Vienna Report, 1873. 



1 86 STEAM ENGINES FOR 

ders in series. The third principle permits an estimate to 
be made of the probable internal wastes of the series, and 
the probable total expenditure of heat and of steam, and a 
solution of all problems of efficiency for the compound 
engine, of whatever type. 

The first step in the process is evidently the determination 
of the best ratio of expansion, under the assumed conditions 
of operation and for the given type of engine, for a single 
cylinder ; then the best ratio of expansion for the series, all 
things considered ; this study being made from the financial 
standpoint, as must be every problem which the engineer is 
called upon to solve. It is not the thermodynamic, nor the 
fluid, nor even the engine, efficiency, which must be finally 
allowed to fix the best ratio of expansion ; but it must be 
the ratio of expansion at maximum commercial efficiency ; 
that which will make the cost of operation at the desired 
power a minimum for the life of the system.' The total 
ratio being settled upon, and that allowable, as a maximum, 
for the single cylinder, it is at once easy to determine the 
best number of cylinders in series. The first-mentioned 
ratio is that at maximum commercial efficiency, as just 
stated ; but the second must be taken as that which gives 
the highest efficiency of engine ; the back-pressure in that 
cylinder, and the friction of the cylinder, taken singly, being 
considered, together with its proper proportion of the friction 
of the engine as a whole. 

The extent to which expansion may be economically car- 
ried in a single cylinder will vary somewhat with the initial 

I. See papers by the author, on the efficiencies of engines, as per references 
already given ; and Manual of the Steam Engine, Vol. I., Chap. VII. 



ELECTRIC LIGHTING PLANTS. 187 

temperature and pressure, and with the physical condition 
of the working fluid ; but it may be taken as ordinarily not 
less than two-and-a-half expansions for unjacketed engines 
with wet steam, and three or four for the better class of 
engines. The total expansion ratio thus becomes, for sev- 
eral types of multi-cylinder engines, as below ; 

MULTI-CYLINDER ENGINES. 

No. cyls. I 2 3 4 

r 2.5 to 3 6.25 to 9 16 to 27 40 to 81 

^1 25 to 30 lbs. 60 to 100 lbs. 120 to 300 lbs. 350 to 800 lbs. 

Expansion is here assumed to be approximately hyperbolic, 
and the terminal pressure to be eight or ten pounds per 
square inch. General experience to date thus indicates 
that a triple expansion engine should do best work up to a 
pressure of about /i = 150 to 250 pounds, and that the four- 
cylinder engine should be adopted from that point up to the 
highest pressures likely to be adopted in the steam engine, 
the double expansion compound serving its purpose well 
below the lowest figures above assigned to the triple engine. 
Any of the four types of engine may be made to overlap the 
range assigned that case by suitably providing against wastes 
occurring within the engine by increased speed, by super- 
heating, by expedients giving higher effectiveness to the 
jackets, or other methods of improvement. Any system 
which increases the efficiency of the simple engine will im- 
prove the efficiency of the compound, and will correspond- 
ingly increase the range of pressure through which it will 
give satisfactory gain as compared with the former. 

The influence of the several economical expedients rec 



STEAM ENGINES FOR 



ognized as useful in other forms of engine, such as super- 
heating, jacketing, and high speed of engine, may readily 
be perceived when the method of operation of the multi- 
cylinder engine is understood in its relations to heat-trans- 
fer and heat-transformation. We may consider them in 
their order : — 

Superheating the steam transferred from boiler to en- 
gine results in the supply of a fluid which may surrender a 
certain portion of heat, measured by the product of its spe- 
cific heat as a gas into the range of superheating and into 
its weight, to the metal of the working cylinder without the 
production of initial condensation. If this quantity is equal 
to or greater than the loss of heat during expansion and ex- 
haust, there will be no initial condensation, and the waste 
from the high-pressure cylinder will be nearly that due to 
the passage of a gas through it under similar conditions of 
temperature and expansion, a comparatively small quantity, 
since any substance in the gaseous state possesses low con- 
ductivity and slight power of absorption and storage of 
heat. Should the superheating be in excess of this amount, 
the steam will not begin to condense until a later period, 
perhaps not at all, the only demand being now for heat 
to supply the amount required to keep the steam dry and 
saturated while expanding and doing work. If the super- 
heating be less than the first - mentioned quantity, ini- 
tial condensation will be reduced, but not entirely pre- 
vented. In any case, the quantity of heat represented by 
the superheating will be a gauge of the amelioration of 
wastes by internal transfer of heat in every cylinder of 
the series. The steam leaving the high-pressure cylinder 



ELECTRIC LIGHTING PLANTS. 189 

will be to that extent dryer than it would otherwise be ; 
and this will be true of the succeeding cylinder or cylin- 
ders. 

Were there no other disappearance of heat than that due 
to cylinder condensation, superheating at the first of the 
series would give superheating at each of the others. In so 
far as condensation doing work, such as was pointed out by 
Rankine and Clausius, takes effect, and so far as other 
wastes by transfer without transformation occur, to that ex- 
tent will the gain, as observed in successive passages from 
cylinder to cylinder, be reduced ; though the improvement 
of the working conditions above asserted will be none the 
less real. Each cylinder will have wetter steam than the 
preceding, in proportion as the condensation doing work 
and the losses by conduction and radiation increase, as a 
total, cylinder by cylinder. 

Steam jacketing, the expedient devised by James 
Watt, for the very purpose of reducing wastes by internal 
condensation, a phenomenon of which he was the discov- 
erer, is a method of approximately " keeping the cylinder as 
hot as the steam which enters it," as Watt put it, in order 
that no such chilling of the entering steam may occur. We 
are interested in the answer to the question: To what extent 
and in what manner is the jacket advantageous in the com- 
pound or multi-cylinder engine ? Authorities disagree, even 
where they have themselves had large practical experience. 
It is sometimes advised to jacket only the high-pressure 
cylinder; sometimes to jacket only the low-pressure cylin- 
der, and sometimes to jacket the whole series, whether one, 
two, or three or more. The philosophy of the multi-cylin- 



ipo STEAM ENGINES FOR 

der engine, as above outlined, would obviously indicate 
that, to secure maximum good effect, assuming the jacket 
on the whole desirable at all, the best system is the lat- 
ter, and that, since the waste of the engine is measured 
by the waste of its most wasteful member, to omit the jacket 
from any one cylinder insures that the aggregate loss of heat 
in the whole engine will be increased by just the amount by 
which waste is increased in that one cylinder by such omis- 
sion. 

It is readily seen, however, that, to secure maximum effi- 
ciency, it is as essential to jacket the cylinders of the com- 
pounded engine as that of the simple engine. The question 
which actually arises in practice, for the designing engineer, 
is whether it will pay to jacket at all or not. It can at 
once be seen that it is not as important, in a financial 
sense, that the multi-cylinder engine be jacketed as it is 
to jacket a simple engine of similar range of expansion. 
The value of the waste due to omission of the jacket is 
less as the number of cylinders is the greater, and is the 
less on any one cylinder as the expansion in that cylinder 
is a less proportion of the whole. It is also seen that 
those conditions which may make it undesirable, as a mat- 
ter of finance, to jacket the simple cylinder, make it still 
less desirable in the compound or multi-cylinder engine. 
As piston speeds are increased, for example, the necessity 
of the jacket decreases and the limit at which it will pay 
to dispense with it is sooner reached in the multi-cylinder 
than in the single-cylinder engine. It is this principle 
which justifies the now not uncommon practice of omit- 
ting jackets from marine engines which are driven up to 



ELECTRIC LIGHTING PLANTS. 191 

1,000 feet a minute; while pumping engines, in which the 
speed is always very low, must usually be jacketed if high 
duty is demanded. 

High engine-speed, the most modern device for reduc- 
ing internal wastes, as well as for decreasing costs of engine 
construction and weights of machine, is evidently a mat- 
ter of less serious importance as the number of cylinders 
is increased; yet it is equally evident that, to secure max- 
imum efficiency, it is essential that the time of exposure 
to the action of the wasteful influences in any one cylin- 
der be made a minimum. At modern and customary 
speeds of piston and of rotation, the value of this, as well 
as the other expedients for improving performance, is much 
less than formerly. 

Non-conducting cylinders, such as were partly se- 
cured by Smeaton by the use of his wood-lined pistons 
and heads, and such as have since been sought by Emery 
and others ; such as was shown to be needed by Watt, 
and later more conclusively by Rankine and his successors; 
would do away with the necessity of compounding on the 
ground of thermodynamic gain ; but would leave the ad- 
vantages of the multi-cylinder engine, on the score of bet- 
ter division of stresses and work, unaffected. What may 
be done in this direction, it is as yet impossible to judge; 
but it is not likely that the device of Smeaton can be made 
successful at modern temperatures and pressures, or in pre^ 
ence of superheating; the plan of Emery of using glass, 
enamel, or other superficial covering of the exposed sur- 
faces, has not yet given promise of success, and nothing as 
yet tried seems to give promise of meeting the requirements 



192 STEAM ENGINES EOR 

of the case.' The value of even an approximately non- 
conducting covering of such nature would be considerable 
for the compound engine, and very great for the simple 
engine; especially for the smaller sizes in which the pro- 
portion of exposed surface is comparatively large. 

Conclusions would thus seem justified as follow : Under 
similarly favorable conditions we may, with equal Hkelihood,. 
anticipate a probability that we may obtain better work with 
multi-cylinder engines in somewhere about the following 
proportion for good examples : 

Gain, Gain, 
Engine. Steam Consumption. Total. Dili. 

Small Large 

Engines- Engines. 

Simple i-cylinder Per I. H. P. 40 lbs. per hr. 20 lbs. 

Compound (double expansion). 30 16 ■20% -2.0% 

Triple expansion 20 14 30 10 

Quadruple expansion 18 12 40 10 

Quintuple expansion 16 11 50 10 

The first three cases are based upon what is. probably 
ample experience ; the last two are obtained by inference 
from the rate of progression thus established, checked by 
computation, assuming that the loss is reduced in propor- 
tion, approximately, to the number of cylinders in series. 
The probable cost of adding one and another cylinder to 
any given type is easily ascertained by the engineer ; he 
knows the cost of fuel and oil ; the value of capital is as 
easily ascertained ; and he can then readily determine 
whether the gain fairly to be anticipated is sufficient to 

I. The author has recently secured an invention devised by himself, consisting 
in the solution of the exposed metal surfaces, leaving the carbon of the casting to 
form a layer resembling vulcanized rubber, which is to be saturated by drying 
oils, solutions of gum or other non-conductor, the covering so formed being inte- 
gral with the cylinder-head or other part. 



ELECTRIC LIGHTING PLANTS. 193 

compensate the cost of its acquirement and to give a fair 
margin of profit. 

Another important inference from what has preceded is 
that the question of use of one or another type of multi- 
cylinder engine is not primarily settled by the magnitude of 
the steam pressure to be adopted ; although it is well settled 
by experience and by the financial aspect of the question, 
as just indicated, that it will not pay to compound a machine 
working at very low pressures ; nor to adopt a third cylinder 
until the pressure approaches, perhaps, four or five atmos- 
pheres, the advisability of adding cylinder after cylinder 
being measured by the rise in pressure, at the rate of not 
more than one cylinder for each four or five atmospheres 
pressures. Whatever the pressure, however, the compound- 
ing will divide the total thermal loss by internal wastes, ap- 
proximately, by the number in series ; but it does not at all 
follow that the efficiency of engine or the commercial effi- 
ciency will be reduced in similar ratio. On the contrary, it 
will never pay to carry the complication as far as the study 
of the ideal case would dictate. The discrepancy will be 
found to be the greater as the real engine the more closely 
approaches ideal perfection, the simple engine becoming the 
more desirable type as the efficiency of it and of each of the 
several elements of the compound engine becomes greater. 

As respects size, it is now easily seen that the gain by com- 
pounding is, so far as the considerations here studied are 
concerned, at least, likely to prove even more marked with 
small than with large engines ; although it may not be, 
commercially, as desirable to adopt this complication. As 

the wastes are invariably, under similar working conditions, 
13 



194 STEAM ENGINES FOR 

greater as size decreases, the desirability of reducing the 
magnitude of those losses would seem likely ordinarily to 
be made the greater, also, as size of engine diminishes. 
With equally dry steam from the boiler, the moisture in the 
steam and the losses by internal condensation are the larger 
as the power supplied and the magnitude of the engine 
furnishing it become less. That experience is showing this 
to be the fact is evidenced by the steady progress made by 
builders of small engines in the introduction of the com- 
pound engine into the market. In the case of the adapta- 
tion of this system to small engines, the effect of cylinder 
condensation remains in each cylinder, well marked, ordi- 
narily, as is seen in the hitherto unnoticed effect observable 
where such small engines are constructed of the Wolff type ; 
and the first effect of the cooling action of the metal upon 
the entering steam is shown by the sudden drop of pressure 
between the two cylinders, at the moment of opening com- 
munication, the fall being like that seen when exhaust 
occurs into the atmosphere from a high terminal expansion, 
and amounting, often, to several pounds.^ 

Problems relating to the efficiency of the multi- 
cylinder engines may be solved most simply by the processes 
devised by the author in modification of the method of 
Rankine, originally applied to the study of the ratio of ex- 
pansion at highest efficiency of capital.'' The number of 
cylinders or of grades of expansion being in all such cases 
settled by general experience and the judgment of the de- 



1. This has been noticed and provided for by the designers of the familiar 
type of single-acting compound. 

2. See IVEanual of the Steam Engine, Vol. I., Chap. VII. 



ELECTRIC LIGHTING PLANTS. 195 

signing engineer, the best ratio of expansion and the best 
proportions of cylinders are readily determined for any 
given case by first obtaining the true Curve of Efficiency 
.for the given class of engines, and then, knowing the prob- 
able back-pressure to be met with, either by custom or by 
taking it with reference to the best relation of initial to final 
pressure, and computing the constant and variable costs of 
operation, solving the problems, in their proper order, by 
a graphical construction which the author has shown to be 
easy and accurately made.' It is enough to say here that 
these best ratios will often be found, for the better class of 
engines employing dry or slightly moist steam, to be not far 
from one-half the ratio of initial to back-pressure, the latter 
including the friction of engine ; and for those of the very 
highest class, using thoroughly dry or superheated and re- 
heated steam, on the system adopted by Cowper, Corliss, 
and Leavitt, this best ratio may be raised economically, on 
the whole, to about two-thirds the ratio of initial to back- 
pressure. 

It is safer, however, to endeavor to find the real curve of 
efficiency for the class of engine considered, and use that 
curve in the solution of the problems of the efficiency of 
fluid, of efficiency of engine, and of efficiency of plant. It 
thus becomes easy to ascertain the best ratios for highest 
duty, for best financial results as designed, as for best 
commercial returns should the opportunity offer of utilizing 
more power than is at first anticipated. 

Proportions of cylinders and relative ratios of 

I. The Several Efficiencies of the Steam Engine. Jour. Franklin Institute, 
May, 1882. 



196 STEAM ENGINES FOR 

EXPANSION in the several cylinders of the multi-cylinder 
engine may readily be settled when the total ratio and the 
total power demanded are determined and exactly pre- 
scribed. It will be found that the total ratio will be made, 
usually, not far from equality in the several cylinders, and 

r = ri"; 

where n is the number of cylinders adopted, r the total ratio, 
and rj the ratio for one cylinder. It will, however, for best 
effect, on the whole, be properly advisable to adopt a com- 
promise between the various modified and conflicting values 
prescribed by the conditions that the work, the effective ini- 
tial pressures, and the several products of range of tem- 
perature into exposed areas, shall be as nearly equal in all 
cylinders as possible. To meet the first condition we must 
have such a ratio in each cylinder as shall make the work 
in each equal to the total net power of the engine divided 
by the number of cylinders in series ; to meet the second 
condition we must make the initial pressure in each such 
that the total range of pressure may be equal to a common 
range in each multiplied by the number of cylinders ; while 
to make the stated products equal throughout the series 
we must have varying differences of pressure, the high- 
pressure cylinder having the maximum range, and the low- 
pressure cylinder the minimum range of pressure. The dif- 
ferences in this latter respect are, in engines using very 
high steam-pressures, quite considerable. Where the steam 
is dry, the speed of engine high, and the jacketing effective, 
this is a matter of less consequence than approximately 
uniform division of work and stresses on the crank-pins. 



ELECTRIC LIGHTING PLANTS. 197 

It is by the application of the principles which have been 
so fully described above that the steam engine for electric 
lighting purposes has been of late so greatly improved in 
respect to its economy of fuel and steam. The gain by 
compounding the smaller engines is so much greater than 
with the larger and originally more economical simple 
engines, that the disadvantage under which the high-speed 
engine has in some respects labored is to a considerable 
extent removed ; and, among compound engines, all the 
common types are more closely competitive. All are ap= 
preaching more and more a common ideal. 

An often minor, yet real and sometimes important, ad- 
vantage of multiple-cylinder engines is their greater free- 
dom, with very high boiler-pressures especially, from liabil- 
ity to give trouble in lubrication. The steam-cylinders are 
the easier to lubricate as the range of pressure within them 
is less. 

The " TANDEM " ENGINE is perhaps the most common 
form of stationary compound engine. In this type, as 
shown in the accompanying illustration, the two cylinders 
are set in line, have a common piston-rod, and drive the 
same crank. The high-pressure cylinder is commonly 
placed behind the low-pressure, and the latter is directly 
attached to the frame of the engine. The exhaust of the 
smaller cylinder is carried in any convenient manner to the 
large engine ; but the more direct and the larger the con- 
duits employed the better. In some cases the two cylin- 
ders are set directly in contact. This plan involves a 
difficulty, usually, in packing the rod between them, but it 
has the advantage of great compactness. 



198 



STEAM ENGINES FOR 




ELECTRIC LIGHTING PLANTS. 1 99 

The compound corliss engine was first introduced 
by other builders ; but no one was more successful in the 
economical working of the machine than was its great orig- 
inator, the late George H. Corliss. The usual method of 
compounding this engine for stationary purposes is that 
known as the " tandem " system, in which the high-pressure 
cylinder is set behind the low-pressure, both pistons having 
a common rod and driving a common set of reciprocating 
parts and having valve-gearing actuated by the same eccen- 
tric and rod. The plan is simple, inexpensive, convenient, 
and compact, and is found to be very satisfactory in opera- 
tion, the economy attained by it being about as high as that 
of any other arrangement yet devised. This method is 
illustrated by the illustration, which exhibits a form of the 
engine designed by Mr. Edwin Reynolds. It is readily 
seen that it would probably be impossible to find a better 
method of combining maximum efficiency with minimum 
cost of construction than this, or to make a more compact 
disposition of parts. It is necessarily of considerable 
length, but in other directions has no greater dimensions 
than the single engine of the simple type. 

The performance of this type of engine has been most 
excellent. For example, the engines of the Nourse steam- 
mill, as constructed by Mr. Corliss, were found to demand 
no more than 1.62 pounds of good fuel per horse-power 
and per hour. The same engine as a simple engine, the 
high-pressure cylinder disconnected, if equal to the best of 
its class, under similar conditions of operation would 
probably not require less than two pounds ; which may 
be taken as about the limit of economical working for 



STEAM ENGINES FOR 



that type of engine with a good condenser and dry- 
steam. 

One disadvantage of this type of engine— the " tandem " 
— is the length of passage between the exhaust-port of the 
high-pressure and the induction-passage of the low-pressure 
cylinder when tlie former is taking steam in the backward 
stroke ; but this is at least partly compensated by the very 
short passage obtainable for the opposite movement. The 
valve-gearing is commonly the same on both cylinders ; but 
it is often so arranged that the governor operates on the 
one cylinder only, leaving the ratio of expansion of the 
other to be determined by the measure of expansion in the 
first. 

Another not uncommon system of compounding this en- 
gine, especially for large powers, is oftener practised in 
Europe than in the United States; this is the coupling of 
two engines, side by side, as in common marine practice ; 
while another method sometimes adopted is the adaptation 
of two independent engines of properly adjusted sizes to act, 
the one as the high-, the other as the low-pressure engine of 
a compound system. These engines are occasionally set at 
some distance apart, when the local conditions make that 
a more convenient disposition. The efficiencies of these 
several types of compound Corliss engines are substantially 
the same. They are all subject to about one-half the inter- 
nal wastes of the simple engine of similar dimensions, to 
about double the external wastes of heat, and have a trifle 
more friction. On the whole they will ordinarily give an 
increased economy amounting to about twenty per cent of 
the heat and fuel consumption of the simple engine. 



ELECTRIC LIGHTING PLANTS. 



In some cases the arrangement of a pair of complete en- 
gines, of properly selected sizes, in such manner that either 
the exhaust of one may be used in the other or steam may 
be taken direct from the boiler to either is found advanta- 
geous. When less power is demanded, or when one is dis- 
abled, the available engine may then be used alone. Econ- 
omy has been attained by this plan, even when the two 
engines are placed at considerable distances apart, the 
precaution being taken to carefully guard against loss of 
heat between them. 

The " CROSS-COMPOUND " type of Multiple-cylinder En- 
gine is illustrated by the accompanying sketch of a pair 
designed by Mr. Reynolds and built by Allis & Co. for the 
Namquit Mills. The cranks are set at right angles, and the 
receiver is placed beneath the floor. This is a less common 
variety than the "tandem "form, but is still often adopted. 

The general arrangement and disposition of the parts of 
a triple-expansion engine, as built by the Corliss Co., are 
seen in the next figure. Here the low-pressure cylinder is 
divided, one of its two elements being coupled with the 
high-pressure cylinder on the right, and the twin with the 
intermediate cylinder on the left. The cranks are set at 
90°. These engines have cylinders 20, 34, 2)^^ and 36 
inches diameter, and 5 feet stroke of piston. All cylinders 
are completely steam-jacketed, heads included, and the 
steam is somewhat superheated. Jet-condensers are used. 
The capacity of the engine is 1,000 I. H. P. or more, and its 
" duty" is about 135,000,000 pounds ; the fuel used, when 
of good quality, amounting, on test, to 1.44 pounds per 
horse-power per hour. 



STEAM ENGINES FOR 




ELECTRIC LIGHTING PLANTS. 



203 




204 STEAM ENGINES FOR 

" Compounding " simple engines is often a very eco- 
nomical and profitable plan. The method depends mainly 
upon the design of the engine to be so altered. The com- 
mon forms of stationary beam-engine are commonly im- 
proved by what is called " McNaughting," placing a new 
high-pressure cylinder beside the old cylinder and connect- 
ing it to the beam either at the old air-pump center if con- 
densing, or to the point at which an air-pump might have 
been attached, if the engine be non-condensing. The ver- 
tical marine engine may sometimes be altered into the 
compound form by placing the new cylinder above the old 
and the two pistons on a common rod. 

The straight-line engine. — Since the first introduc- 
tion of this engine in 1880 there have frequently been made 
improvements in the details of construction and two im- 
portant changes in steam-distribution. 

In the use of constant lead and the specially devised 
valve- motion to accomplish it, it was discovered that a con- 
stant lead was not a desirable thing, and that changing 
to a variable lead (the reverse of that which obtains in 
locomotive practice) was very much of an improvement. 
By giving considerable lead to the valve when the engine is 
doing most work the machine is found to run more quietly 
and to do more work with the same steam-consumption ; 
when running light a noticeable negative lead also secures 
quiet running as well as a more economical use of steam. 

In the first case increased lead gives more compression 
and a freer exhaust, both of which are desirable ; and in 
the case of a light load, when the compression (with a 
single valve) is too great in any event and the exhaust too 



ELECTRIC LIGHTING PLANTS. 205 

early, the changing of positive lead to negative reduces the 
compression and prolongs the exhaust. 

Further than this — to utilize a principle made prominent 
(if not discovered) by Willans in his extended experiments, 
that after a certain point of cut-off is reached it is more 
economical to reduce the pressure than to increase the 
number of expansions, as would be the case if the cut-off 
was made shorter ; and in correspondence with experiments 
made by Mr. E. J. Armstrong in conjunction with Mn 
Sweet — further changes have shown that it is possible to 
accomplish the result with the single valve. The card 
below, taken with a variable load, shows to what extent this 
has been carried. 




Straight-line Diagram. 

Another change recently made has been the introduction 
of a separate exhaust-valve, making the steam-distribu- 
tion nearly the same as in the Porter-Allen engine except 
that the cut-off is carried through a wider range, varying 
from three-quarter stroke to zero, and, too, the lead is 



2o6 STEAM ENGINES FOR 

varied from positive to negative as the cut-off is reduced, 
insuring still running at both light and heavy loads. 

The Compound Form of the Sweet engine is one of the 
best of illustrations of the compactness which may be 
given the " tandem " type of the machine. The engine is 
built, as to its high-pressure cylinder and working parts, 
precisely like the standard type of the simple engine of the 
same design. It has exactly the same characteristic form 
of frame and methods of connection and of steam-distribu- 
tion and governor. Directly behind the high-pressure 
cylinder, however, is placed the larger, low-pressure, cylin- 
der, the whole forming practically one structure. The 
whole machine can be taken apart and reassembled without 
disturbing the cylinders or the frame. Both pistons, which 
are mounted on one rod, can be removed and replaced, 
the intermediate head coming away with its stuffing-box 
through the larger cylinder. The packing of the rod be- 
tween the two cylinders is a metallic sleeve, solid and free 
from liability to produce trouble or to require readjust- 
ment, once in' place and properly fitted. It is free from 
liability to wear or to bear upon the rod in such a manner 
as to produce undue friction and heating, while it is loose 
enough to work smoothly, and yet tight enough to prevent 
leakage of steam past its shell. The valve of the low-pres- 
sure cylinder is worked by an independent, fixed, eccentric, 
and the expansion is adjusted by the action of the governor, 
affecting the point of cut-off on the high-pressure cylinder, 
precisely as in the simple engine. Where the load is fairly 
steady this arrangement is perfectly satisfactory. The in- 



ELECTRIC LIGHTING PLANTS. 



207 




208 



STEAM ENGINES FOR 



ventor has also planned a triple-expansion vertical engine 
of equal simplicity. 











i / < 



The armington & sims engine was among the first of 
the " single-valve automatic " engines to find a place in 



ELECTRIC LIGHTING PLANTS. 209 

electric lighting, and it was also one of the earliest to be 
built as a compound engine. An experimental engine was 
built about 1880 ; but the engine was not constructed as a 
multiple-cylinder engine regularly and as a standard type 
until some years later. The form given this engine is seen 
in the accompanying illustration, which represents the ma- 
chine as constructed to give 100 horse-power at high speed. 
The regulation and the general construction of each of the 
two elements of the compound engine are similar to those 
already described in the simple engine. The two cranks 
are placed opposite, and this gives that perfection of bal- 
ance which cannot be secured by any other device. It is 
also the best method of obtaining transfer of steam from 
the one engine to the other with minimum loss of pressure. 
The attainment of a speed of 800 revolutions a minute 
is possible. Both cylinders are steam-jacketed. Such 
engines are usually made up to about 200 horse-power. In 
the type here shown, the cranks being opposite, the engine 
balanced, it can safely be run at a high speed ; the peculiar 
form of the valve provides for quick admission of steam, 
and the large wearing-surfaces insure it more or less fully 
against leakage ; the pistons and stuffing-boxes used are 
more easily got at than ordinarily with engines of the 
" tandem " type. 

One of the earliest to adopt compounding as a system of 
standard construction was Mr. Thompson in the " Buckeye " 
engine in 1879. This engine, tested by Mr. Barrus, gave 
an economy measured by 19 pounds of dry steam per 
I. H. P. per hour. The gearing lends itself readily to any 
type of construction, and the engines are built in three 



2IO 



STEAM ENGINES FOR 




ELECTRIC LIGHTING PLANTS. 



classes, ranging from what are now considered low to toler- 
ably high speeds. The figure shows in section the arrange- 
ment of cylinders and valves and connections in the " tan- 
dem-compound " engine, a form commonly employed 
because of its simplicity and cheapness, compactness and 
freedom from liability to derangement. In many of these 
engines piston-valves are used when steam-pressures are 
very high. 

In the drawing are well shown the small clearance char- 
acterizing this form of cylinder and valve. In this, as in 
the previously described forms of the same engine, constant 
travel of the valves, giving freedom from leakage, and a 
wide range of expansion if needed, can be secured within 
any reasonable limits. 




Tandem COMPOUND Engine and Dynamo. 

The " Ideal" is a more recent development of the Ide 
engine, and involves particularly the self-oiling system al- 
ready described in the case of the Worthington engine. 



STEAM ENGINES FOR 



The problem which designers must here solve is that of 
combining effective lubrication with neatness. 

They have here not only secured copious lubrication, 
flushing the bearings in oil, but have attained a degree of 




cleanliness and freedom from throwing oil over the parts of 
the engine or floor that cannot be equaled by the older 
tvpe. With a " bath " system of lubrication — bearings 



ELECTRIC LIGHTING PLANTS. 



flushed in oil — we overcome the principal objections that 
have been urged against the life of high-speed engines in 
addition to the excellent running balance attained in the 
latest product, resulting in cleanliness and quiet running, 
and the ability to run the engines for an indefinite time 
without stopping/ 

The following are the principal dimensions of this engine 
with 400 K. W. General Electric generator attached, running 
non-condensing. 

COMPOUND DIRECT-CONNECTED ENGINE. 

Cylinders 19" and 32" by 42". 

Speed 100 revs. 

Weight of fly-wheel 43,000 lbs. 

Diam. of crank-shaft 18", steei forging. 

Crank-pin 9" X 9". 

Cross-head pin 6" X 7". 

Connecting-rod 5^" cranks. 

Cross-head shoes, phosphor-bronze, 12" X 24". 

Piston-rods i\" and 4^". 

The high-pressure valve is actuated by an automatic gov- 
ernor, the same type as in the Ideal engine. 

The high-pressure valve is the Ide adjustable piston-valve. 

The low-pressure valve is actuated by independent ad- 
justable eccentric. 

The low-pressure valves are of the Porter-Allen type, 
provided with pressure-plates. 



I, See Friction and Lost Work in Machinery and Millvvork.- R. H. Thurston; 
N. Y., J. Wiley & Sons. 



2 14 STEAM ENGINES FOR 

pjach cylinder is provided with 2 1" automatic relief-valves. 

Weight of engine 145,000 lbs. 

A good idea of the disposition of parts in the tandem- 
compound engine is obtained from the sketch. 

The next figure represents an automatic compound engine 
designed by Mr. F. H. Ball especially for use in driving dy- 
namo-electric machinery. 

The illustration represents an engine using steam at 125 
pounds pressure and of 250 horse-power. 

It was thought best to build these engines in the form 
of a double engine rather than the " tandem " type of com • 
pound, because it was believed that higher rotative speed 
could be successfully used where the v.^ork was distributed 
over two sets of crank-pins and journals of smaller sizes, 
rather than with the use of a single set of bearings of 
larger size, as in the case of a tandem engine developing 
the combined power of the double compound. 

The cylinder dimensions selected after working up a large 
number of provisional diagrams were as follows : 

High-pressure cylinder : diameter 13"; stroke 16". Low- 
pressure cylinder: diameter 25" ; stroke 16". 

The maximum power attained on trial was 325 1. H. P. 

The next figure illustrates the same make of engine com- 
pounded in the more usual way, a " tandem "-compound 
high-speed engine for electric lighting or other purposes, 
which is found to be one of the best combinations of 
efficiency with simplicity and small cost. 

Nearly all makers now use this method of compounding 
for all cases except where, as in marine engines, a double 
engine with cranks at right angles is considered desirable on 



ELECTRIC LIGHTING PLANTS. 



215 



Other grounds. They are nearly as simple in form, as cheap 
of construction, and as inexpensive in repairs as the simple 
engine. 




The methods of construction and of setting up a gov- 
ernor are well illustrated in the case of the Ball governor, as 



2l6 



STEAM ENGINES FOE 



seen in the figure. The eccentric ^4 is a small disk solidly 
bolted on the end of the wheel-hub, and as small and light 




as is consistent with satisfactory operation. The strap B 
is, as usual, in halves, but it is held in place by a thin disk, 



ELECTRIC LIGHTING PLANTS. 



217 




Ball's Governor. 



2l8 



STEAM ENGINES J- OR 



C, on one side and the not uncommon flange on the other. 
Links, DL, connect the strap and the weight sof the gov- 
ernor ; wliile a pin, E, set in the cover-plate, actuates the 
valve as usual. The center of the eccentric is so located 
that its motion relatively to the wheel, as produced by the 
governor, causes E to describe an arc about the eccentric- 
centre giving the desired variation of cut-off with nearly 
constant lead, except at very high ratios of expansion, 
where the lead is rapidly taken off. When the engine is 
subject to irregular changes of speed due to inertia or gravity 



S50 




Triple-expansion DiAokAM. 

in the governor, the dash-pot should be introduced as in the 
illustration. The method of assemblage is well shown by 
the peculiar method of engraving the latter figure, a method 
introduced by Westinghouse. 

The diagram here reproduced illustrates a good adjust- 



ELECTRIC LIGHTING PLANTS. 219 

ment of such a valve system, and was taken from an 
engine, designed by Mr. Ball, having four cylinders and of 
the triple-expansion type, placed in their proper order of 
relation and reduced to. a common scale. The ranges of 
temperatures in the several cylinders are also exhibited at 
the left. In each cylinder the compression is adjusted, 
as seen, to fill the clearance-spaces, and no appreciable 
"drop" takes place. The two low-pressure cylinders de- 
velop nearly the same amount of power as the high-pres- 
sure, and the latter about 0.7 as much as the intermediate 
cylinder. The upper line shown exhibits the steam-chest 
pressures and the loss due to the throttling action of a long 
steam-pipe. 

The shaft-governor is a " safety-governor," and if any 
part breaks or becomes deranged in any way the result is 
to stop the engine. The use of the dash-pot was probably 
resorted to at an early date for the purpose above de- 
scribed. 

Messrs. Mcintosh & Seymour have also devised an inter- 
esting modification of the Hartnell type of governor. This 
is shown in the figure, page 220. It consists of a pair of 
pivoted weights, one of which is shown separately at A^ 
having inclined jaws, in which slide two blocks. These 
blocks turn freely on a boss upon the pendulum, shown on 
B, to which the eccentric is attached, and which is free to 
swing across the shaft. The pendulum is pivoted in such a 
way that while the cut-off changes from five-eighths to zero 
the steam-lead does not vary. The inclination of the jaws 
in the weights is such that, through the action of friction, 
their position is not influenced by the action of the valve 



STEAM ENGINES FOR 




McIntosh & Seymour Governor and Details. 



•^ 




ELECTRIC LIGHTING PLANTS. 221 

and rod, and yet they are always in statical equilibrium 
and have no tendency to race. The spring bears upon the 
weights through the hardened-steel pins, one end of each 
pin resting in a hardened cup on the end of the spring and 
the other in a slot in the weight. These slots are made 
deep, so that the pin bears upon the center of gravity of 
the weight, and the pressure of the spring directly opposes 
the centrifugal force. 

The arrangement of the governor on the engine is seen 
in the accompanying full-page engraving of the tandem 
compound of this make. 

The engine itself illustrates a now standard construction. 
The high-pressure cylinder and the receiver are jacketed. 
The two valves are placed on opposite sides of the engine 
to secure direct connection and accessibility. The receiver 
takes jacket-steam from the high-pressure cylinder jacket 
and returns all water of condensation to the boiler. The 
governor system actuates the high-pressure valve, the low- 
pressure eccentric being fixed. The general proportions of 
parts can be judged from the illustration. 

An ingenious modification of the enclosed single-acting 
compound type of engine, the " central-valve engine " of 
Mr. Willans — which is also interesting as having been the 
subject of exceptionally complete scientific investigation 
— is seen in this figure.' It was studied as a simple, a 
compound, and a triple-expansion engine, being easily 
adapted to either system. 

As here shown, its three cylinders are placed in series 



I. The discussion of this paper is remarkably interesting. Trans. Brit. Inst. C. 
E., March, i888; 1887-18-9; No. 2306, Vol. XCIII. 



STEAM ENGINES FOR 



and "tandem." The valves are on one rod, driven by a 
single eccentric on the crank-pin ; the rod being in the 

axis of the engine and the 
valves within the hollow- 
piston-rod. Cut-off is ef- 
fected by the passage of the 
ports into metallic rings in 
the ends of the cylinders, 
and is adjustable by hand or 
by the governor. Compres- 
sion is effected in the sepa- 
rate cushion-chamber.' 

These engines are usually 
grouped in pairs, with cranks 
at right angles. 

As the valve-faces move 
with the pistons, the valve- 
motion must here be taken 
from the pins to secure the 
desired movement relatively 
to the pistons. The work on 
the main journals and pins is 
substantially all on the upper 
" brass " of the latter and the 
WiLLANs' Engine. (Scale ^V-) ^^^^.g, ^f ^^e ioxmtx, and the 

crank-pin working-side is never expected to leave the pin. 
The eccentric-rod, like the connecting-rod, is always in com- 
pression, and the main bearings also are always under con- 
stant downward thrust. Lubrication is secured, by the 

I. Trans. Brit. Inst. C. E., Vol. LXXXI. p. i66. 




f XNAUST^-h .M> 



ELECTRIC LIGHTING PLANTS. 223 

Westinghouse method, by the dipping of the crank into a 
pool of oil and water in the crank-case. The guide-pistons 
are arranged to produce the needed cushion by compression 
of the air in the compression-chambers, and this is adjustable 
as may prove to be advisable. The governor is of the now 
familiar Hartnell type. 

Multiple-cylinder diagrams take forms as follow : 
In this illustration from Mr. Porter's report ' the natural 
form of the expansion-line in the single cylinder having 
the capacity here observed in the low-pressure engine, 
would be that shown by one or other of the two dotted 
lines, accordingly as the expansion approaches more or less 
closely the hyperbolic form. The initial volume is AB 
and the pressure as shown on the vertical scale, while the 
gradual loss of pressure with increase of volume is shown by 
the two scales as the line progresses toward the right 
to its terminal point at /. The de^'iation from the dotted 
line of the actual expansion-line between B and C illus- 
trates the gain of weight and pressure due to the pro- 
gressing re-evaporation of steam originally condensed in the 
cylinder at the opening of the steam-valve and to the ad- 
mission of the fluid into the colder cylinder. Here expan- 
sion occurs from the initial pressure and volume at B down 
to the terminal point C in the high-pressure, and from C or 
H Xo /in the low-pressure, cylinder. The indicator-dia- 
grams actually obtained are ABCJD and £FG, the latter 
being the equivalent in the low-pressure cylinder of the 
card HI J., which would have been produced had the high- 
pressure cylinder been given sufficient length to permit the 

I. Manual of the Steam Engine, R. H. Thurston, Vol. II. p. 59. 



124 



Sl'EAM ENGINES FOR 



completion of the expansion in that cylinder. The varia- 
tion of the full line, representing the real diagram, from the 
ideal dotted expansion-line is indicative of the fluctuations 



filii 
nil 
nil 
nil 
ini 



II 



B 



M 

liii 



in 
■11 



nn 



inniitsiiii 
imniini 
iininiiP^ 
"iiiisrs^ii 
^sssSfliniii 
nniisgiT'''" 



nn 



n 



ni 
ni 

HII 



nn 



I 



\ 



ir 



nn 
i»^ 



nn 
nn 
iif « .^j 



\ 



\ iti 



t» J «J su|adi 

H!lilSii^i|Pi!|Sill||g|S :: « JS, 



of pressure produced by the condensation and re-evapora- 
tions taking place as expansion progresses in the metallic 
chamber serving as working-cylinder. 

The succeeding figure illustrates the visible differences 
between the diagrams actually taken from the two cylinders 



ELECTRIC LIGHTING PLANTS. 



225 



Of a compound engine— in this case a " Reynolds-Corliss " 
— and the ideal combined card. 



)(!§ 


§ 


g 


g 


^I g| S| 5 


g 


s 









01 



B 
s 













sajnssaid jo aiuog 
ootrej-cop 




•1 










** 


k 








''' 


u 


1' 




1 


^~1-. 


1 1 al i If/ 












■ 1 ~i\ 






10 




"^'^^^^::4-^,^ ; ■■ i c 


' /«l\ 










h^-v^^ 1 H 


1 / i;|j\ 










, >"c;^s.l.. ' !s 


1,- ~ 












'-^"%Nj-'''.^ 


i 


8S139I3J 











^r 


rU3J139tO 


f 

1 


" 


I 






1 




in 








if 






i 
\ 

r 


^ 1 

< 


3 , / 
11 


r* 

3 

CM 


a) 


a 

^ 




i 




g 




1 






OS 


11/ 


?5 










FbsBaia; 


' 










? 



This shows the method of reducing the actual indicator- 
diagrams to the combined form, and the variations from 



226 



STEAM ENGINES FOR 



the ideal expansion-line due to imperfections of the engine 
as a work of human art. Pressures are measured in pounds 
on the square inch and volumes in cubic feet, actual ca- 
pacities of cylinder being given. As shown on the diagram, 




Triple-expansion Diagram. 



about 32- cubic feet of steam enter the high-pressure cylin- 
der each stroke at a pressure of no pounds per square 
inch above vacuum ; it expands nearly adiabatically to 9:^ 
cubic feet, is then transferred to the low-pressure, dropping 
from the terminal pressure, 40 pounds in the high-pressure 
cylinder, to 20 in the low-pressure, and then expanding in 
the latter down to about 12 pounds, it passes into the 
condenser, the back-pressure thus becoming not far from 
an average of 6 pounds. The two indicator-diagrams are 
shown by the ** hatched " spaces ; the ideal diagram en- 



ELECTRIC LIGHTING PLANTS. 227 

closes both, its outline being the dotted lines. The very- 
considerable space measuring the difference of the. two 
areas is a gauge of the imperfection of the cycle. The 
departure of the actual line from the two ideal expansion, 
curves, and the fact that the former lies within both the 
latter, indicate that the jacket does not supply heat enough 
to compensate the condensation of the expanding fluid, far 
less enough to retain its temperature constant or to contin- 
uously superheat it. 

The discordant fluctuations of similar lines in the two 
indicator-diagrams exhibit the effect of non-synchronous 
motion of the two cylinders. 

The last illustration exhibits the proportions of diagrams 
taken from a triple- expansion engine drawn to common 
volume and pressure scales and placed under the Mari- 
otte line. The engine has cylinders having the ratios 
I : 2.25 : 2.42, and the total ratio of expansion is 8, the cut- 
off in the several cylinders being set at 1.47, 1.3, 1.3. An 
advantage of this type of receiver-engine, with its cranks 
making equal angles, is that the drop in pressure may be 
made unimportant. 

In the receiver-engine the less the drop of pressure at 
the end of the stroke, at the passage of the exhaust-steam 
into the receiver, the less the waste. 

The action of the steam and its variations of pressure 
are, throughout the cycle, precisely similar to that in a sim- 
ple engine. Large steam-ports and a good expansion-gear 
bring the steam-line close up to that of boiler-pressure ; a 
well-jacketed cylinder allows the expansion-line to follow 
closely that laid down for the ideal engine ; short and free 



2 28 STEAM ENGINES FOR 

ports between the two cylinders give an exhaust from the 
high-pressure and a supply to the low-pressure cylinder 
which are nearly coincident ; and the two cards would, if 
reduced to a single diagram, exhibit a very close approxi- 
mation to that which would have been constructed as the 
ideal diagram of this class of engine. When these points 
are not well attended to, variations of twenty and even 
thirty or forty per cent may be observed between the com- 
puted power, as based on the designer's indicator-cards 
and the actual work of the engines under their ordinary 
conditions of operation.' 

It has long been known that there may be determined a 
certain definite ratio of expansion in the high-pressure cyl- 
inder of a multiple-expansion engine, such that, at that 
ratio, the mean pressure on its piston is a maximum.' 

Thus, assuming hyperbolic expansion, and taking 

z/j = volume of the h.-p. cylinder ; 
v^ = " " " next " ; 

-i = cut-off in the h.-p. " ; 

r, = ratio of expansion h.-p. cylinder ; 
/j = initial pressure in " " ; 

;>j = /j = pressure at end of its stroke ; 
I -f- ^j = cut-off in the l.-p. cylinder — 



—A P^ — ": — 



1. For a full and clear treatment of this subject in its minor details see D. K. 
Clark's Manual, p. 849 et seg,, or his Treatise on the Steam-engine, 1889-90. 

2. Trans. Inst. Nav. Architects of G. B., Vol. XIX. p. 205. 



ELECTRIC LIGHTING PLANTS. ^^9 

while the work done per stroke is 

which is a maximum when, taking r^ as variable, 

log, r = ^. 

When r^ = i, as in the ordinary engine, we have 
r^ ■= e = 2.718. 

Thus, for example, with cylinders having volumes as 
4:1, r^= 2 ; steam at 80 lbs. pressure, r = 1.65 and 
pm = 45'4 lbs. per square inch. 

This value is somewhat modified by the presence of the 
intermediate passages between the cylinders, a drop occur- 
ring in the pressure at the instant of opening the exhaust 
from the small cylinder ; but this drop is less as those pas- 
sages are larger ; and if forming an intermediate reservoir, 
as is sometimes the case where " reheating '" between the 
cylinders is practised, this loss and the corresponding re- 
duction in the mean pressure obtained, in work done and 
in the actual total ratio of expansion, is sometimes quite 
unimportant compared with the gain by that process. A 
common value for the reduction of total expansion is not 
far from 20 per cent, rising to one-third with small reser- 
voirs and falling to a lower figure with larger spaces. The 
loss of work may usually be neglected. 

The receiver type of engine with equidistant cranks and 
intermediate reservoirs is less seriously affected by inter- 
mediate spaces. The reduction of pressure and the loss of 



230 STEAM ENGINES FOR 

total expansion is but about 10 per cent where the receiver- 
space is equal to the volume of the smaller cylinder, and 
falls to less than 5, in usual cases, when the receiver is 
large. 

The proportions of parts of engines of the " high- 
speed " class have been made a subject of special study by 
Professor J. H. Barr. The mathematical principles of ap- 
plied mechanics and of the strength of material as de- 
veloped by writers on the subject are necessarily accepted 
by the designer with some reservation, since he must de- 
sign his engine for safety, meeting the accidental stresses 
due all forms of contingency to be fairly anticipated in its 
operation with ordinarily good management under average 
working conditions. Original computed proportions are 
thus, in all engineering, subject to continual readjustment 
in the light of experience. The proportions representing 
good average practice are given in the table.' 

It occurred to Mr. Barr that it might be possible to de- 
rive formulas which would express, more or less closely, 
the conclusions arrived at as the result of experience in 
engine-construction. These formulas are empirical in the 
sense that they are adjusted to agree with observations ; 
but they should be rational in form. 

There is a striking general agreement among builders of 
standard engines of each type as to the proportions of 
many parts, making due allowance for differences of con- 
ditions, and practice has settled down to somewhat definite 
lines. 

The data sought were entered on a blank thus : 

I. Trans. A. S. M. E., Dec. 1895, Vol. XVII. No. DCLXXII. 



ELECTRIC LIGHTING PLANTS. 



231 



FORM FOR ENGINE DATA. 

Schools of Mechanical Engineering Sibley College Cornell University, 

and of the Mechanic Arts. Machine Design. 

R. H. Thurston, Director. John H. Barr. 

Data on Steam-engines. 189 . . 



Diameter of cylinder 

Length of. stroke 

Revolutions per minute 

Rated horse-power 

Face of piston 

Diameter of piston-rod 

Material " " " 

Mid-section of connecting-rod . , . 

Diameter of crank pin 

Length " " " 

Area of cross-head shoes 

Diameter of main journal.' 

Length " " " 

Length of shaft, c. to c. bearings. 

Material of shaft 

Diameter of fly-wheel 

Face of fly-wheel 

Total weight of fly-wheel 

Weight of rim of fly-wheel 

Weight of complete engine 



The data obtained in this way were very complete, cov- 
ering 75 engines by 12 builders, the sizes of engines ranging 
from 25 to 225 rated horse-power. 

The following notation is used : 

D = diameter of piston ; A = area of piston ; Z — 
length of stroke ; S = steam-pressure, taken at 100 pounds 
per square inch above exhaust as a standard pressure ; 
H. P. = rated horse-power ; iV = revolutions per minute; 
C = a constant. All dimensions in inches, unless stated 
to the contrary. 

The general method employed in deriving the various 
expressions may be illustrated by reference to that used for 
the diameter of the crank-shaft at the main bearings. 



232 STEAM ENGINES FOR 

Crank-shaft. — d = diameter of shaft. The formula for 
the diameter of a shaft which is subjected to torsion is 
d = Cr H. P. -7- JV, if the moment of torsion is constant. 

The constants found as above give 



d= 7.56 \^H. V. -^ JV for the mean, 
= 8.76 f H. P. -^ jy " " maximum, 



5.98 Vh. p. 



JV " " minimum. 



For example : If an engine develops 100 horse-power at 
250 revolutions per minute, the first of these formulas gives 



d= 7.56^100 ^ 250 =r 7.56 V.4 = 7.56 X.737 = 5.57 

inches, or say 5^ inches. 

The formulas give the range of sizes from 4^^ inches to 6|- 
inches. 

Piston-rod. — The expression is based upon the Euler 
formula for a long strut : P =■ cEI -~ /', in which P is the 
load, E the modulus of elasticity, / the moment of inertia 
of section, and / the length of strut. P is proportional to the 
square of the piston diameter (-^^) for any given pressure. 

/ = -iz'^d" for a circular section; /is taken equal to the 
length of stroke, L. Collecting and solving, 



d = CVdT = CVVL. 

The equation of the mean gives .145 as the value of C, 
while the extreme values are .119 and .177, the minimum 
and maximum values, respectively. 

Connecting-rods are first treated as long struts, then the 
allowance for flexure-stresses due to inertia is examined. 



ELECTRIC LIGHTING PLANl^S. 233 

For resistance to buckling in the plane of motion the con- 
necting-rod is treated as pin-connected or round-ended ; 
for flexure in a plane at right angles to this the strut is 
square-ended. Hence (neglecting inertia) the thickness or 
breadth {b) of a rod of rectangular mid-section should be 
one-half the height iji). The formula for breadth is (^ = 



C^ DL' , in which IJ is the length of the rod. 

The data examined give .0545 as the mean value of 
C, with .0433 and. 0693 as the minimum and maximum 
values. 

The excess of h over 2b may be a provision for stresses 
due to inertia. To show this allowance points were plotted 
having corresponding values of ^and h for the co-ordinates. 
This curve shows that h is from 2.18 to 4 times b, the 
mean value being 2.73-^. 

Main jour?ials. — The length of journal to prevent heat- 

ing is /= C — - — , but the data are insufficient to clearly 

locate the mean. 

For projected area of each bearing dl = C' SA = CA, 
C ranging from .367 to .739, the mean value being .489. 

li,p is the pressure per square inch of projected area, 



_ ^ , 2pdl dl S 

2pdl — SA ; hence — - — X -^ ox p = —p,. 
^ S C 20 



With steam-pressure of 100 pounds this gives about 100 
pounds as the pressure per square inch of projected area, 
using the mean value of C, while 140 and 70 are the ex- 
treme values of p. 



2 34 STEAM ENGINES FOR 

TJ P 

Crank-pin. — The length of crank-pin is / = C — - — '. The 
equations derived are respectively 



/ H. P.\ , . , 

/ = .2,ZZ\ — J — + 2-2 inches, mean ; 

/FT P \ 
/ = .ipzf — J — ' j -f .88, minimum ; 



maxmium. 



L ] 



The data are insufficient. 

The projected areas of the crank-pins were 

dl = .22 A, mean ; 
= .07^4, minimum ; 
= .44^, maximum. 

These values give (for steam 100 pounds per square inch) 
450, 1,400, and 225, mean, maximum, and minimum, re- 
spectively. 

Face of piston. — A wide divergence was noted in the ratio 
of diameter to face of piston. The following formulas were 
obtained : 

Face = .437/?, mean ; 

= .T,ooD, minimum ; 
= .6$oD, maximum. 

Cross-head pin. — Projected area varies from .066^ to 
.^46 A, the mean value being about d/ = .10^ A. The length 
of pin was from d to 2d, the mean being / = 1.33^. 



ELECTRIC LIGHTING PLANTS. 235 



Fly-wheel. — The weight of rim, W, should be propor- 
tional to ^ ' ^'.. (in which D. is diameter of wheel in 
inches). A wide range of weights occurs here : 

H. P. 

>^ = 833,000,000,000^^3 , mean ; 

H. P. 

= 341,000,000,000— 5— —J, minmium ; 

H. P. 

= 2,780,000,000,000 3 - 3 , maximum. 



General practice lies near the mean. 

The linear velocity of rims was as an average about 4,200 
feet per minute. 

Weight of reciprocating parts. — The weight of recipro- 

eating parts, W, should be proportional to ; . Taking 

the reciprocating parts as made up of the piston, piston- 
rod, cross-head, and one-half the connecting-rod as a mean, 

W= 1,850,0002^,. 

Weight of entire engine per horse-ti07ver. — The average 
weight of engine is 

W = ii7(H. P. — 7), or «^ =: ii7(H. P.) - 820 pounds, 

assuming the steam-pressure 100 pounds per square inch 
above exhaust-pressure. 

The efficiency and economy of this class of engine 
have been already indicated to be superior to the simple 
engine in proportion to the reduction effected in the 



236 STEAM ENGINES FOR 

amount of the internal wastes, very nearly. The economy 
due to placing the cylinders in series has also been seen to 
be, roughly stated, pretty nearly that of the simple engine — 
doing the same work at the same ratio of expansion — 
divided by the number of cylinders in series. The actual 
performance of an engine of good design, operated under 
fairly economical, and perhaps fair average, conditions will 
be given presently. 

The absolute efficiency of the engine, as in all cases, and 
with all classes of heat-motors, is measured by the quotient 
of the work delivered in the assumed unit of time to the 
thermodynamic equivalent of the energy supplied, in steam 
or in fuel, or in thermal units. Thus, if the number of 
B. T. U. be measured per I. H. P. and per hour — since the 
thermal equivalent of the horse-power is 2,545 B. T. U. per 
hour for efficiency unit — the efficiency of the engine tested 
must be 

effic. = 2,545/Zr, 

where H*'va the quantity of heat demanded per horse-power 
and per hour. If W is the " water-rate " of the engine, 
the weight of steam or of feed-water supplied per horse- 
power and per hour under the conditions of the engine- 
trial, and if H^ is the quantity of heat per unit weight ab- 
sorbed from the fuel, the efficiency, gauged by the steam- 
consumption, becomes 

effic. = 2,545/ f^-^; 

as, for example, if the steam take up, in the heater and the 
boiler, 1,018 B. T. U. per pound and transfer it to the 



ELECTRIC LIGHTING PLANTS. 237 

engine, the efficiency becomes, assuming 20 pounds per 
I. H. P. per hour, 12^^, thus : 

effic. = 2,545/20,360 = 2,545/20 X 1,018 = 0.125. 

Similarly, if the fuel has a net value, in heat delivered to 
the boiler and utilized in making steam, of 10,180 B. T. U., 
which is not an exceptional figure, the efficiency becomes. 
at 2 pounds per I. H. P. per hour, 

effic. = 2,545/2 X 10,180 = 0.125. 

The measurement of the indicator-diagram gives the 
quantity of dynamic energy developed, while that of the 
heat supplied by one or another of these methods gives 
the measure of the energy expended. The quotient of 
energy received by energy paid out, measured in similar 
terms, is the measure of the absolute efficiency of the 
system. 

Computations of the probable efficiencies of the 
" Ideal Case " and of the Real Engine, basing the estimates 
of its wastes upon earlier experiments upon the same class 
of engine, are readily made by the methods of Rankine, 
supplemented by those of Hirn, the first to engage in this 
research. 

It is proposed to compute the demand for heat and 
steam for the purposes of designer and purchaser, in the 
case of a simple engine, condensing, with 5 pounds back- 
pressure in the cylinder, on the assumption of the data 
given below ; the conditions as to waste being substantially 
those illustrated in the Sandy Hook experiments of 1884. 



238 STEAM ENGINES FOR 

Pressures are taken from 75 to 155 pounds per square inch 
above the atmosphere, ratios of expansion from 1.6 to 16, 
and the engine as speeded at 280. External wastes of heat 
are assumed to average 0.5 B. T. U. per square foot of ex- 
ternal surface and per degree range of temperature from at- 
mospheric — here taken as 100° F. Internal wastes are taken 
as aggregating, as a fraction of the total steam supplied, 

w =^ a Vrn/a, 

where the coefficient a- = 4 in the case assumed to be fairly- 
representative of that here considered; (/is the diameter of 
cylinder in inches,^ r the ratio of expansion,' and n the 
number of revolutions ^tx second. Friction-wastes are taken 
as found for moderate cut-offs, efficiency of the engine as 
a machine being assumed at 0.85. Better work than this 
can be and should be done. J is taken as 778. The fol- 
lowing are the assumed data: 

DATA. 
Cylinder 6" X 10"; rev. 280; rated 10 I. H. P. 

A = 75 95 "5 135 155' 

/>3 = 5 5 5 5 5 

r = 1.6 2 4 8 16 

_i_5 I I I I 

'^~r~8 ~2 4 8 16 

Pressures are here measured from absolute zero. 

1. Of the low-pressure cylinder in the case of the multiple-cylinder engine. 

2. Of the cylinder of largest expansion in the case of the multiple-cylinder engine. 



ELECTRIC LIGHTING PLANTS. 239 

The work per cubic foot of steam is here computed by 
the familiar expressions of Rankine : 



and 



T-T\I-log. p 



T — T 



r, 



/, = ITDjr. 



An examination of the figures here collected will show- 
in a most interesting manner the gradual variation of steam- 
consumption with change of expansion at each pressure; 
and a comparison of the figure for the several pressures will 
illustrate the interesting modifications of result due to vari- 
ations of expansion with pressures, and the differences in 
the location of the best points of cut-off for these pressures. 
These instructive comparisons are best made by the con- 
struction of curves, of which the co-ordinates are, for each 
pressure, weights of steam demanded per horse-power and 
per hour at stated ratios of expansion. Such figures have 
been obtained by the computers for the present case, and 
are illustrated in the accompanying tables. It is seen that at 
the lowest pressure, 75 pounds, maximum economy of 
steam and fuel is attained at a cut-off very near -g^, or a 
ratio of expansion of about 4.5 when the dynamonietric 
power is taken, or at about a cut-off of 0.2 and r = 5 on 
the basis of indicated power. These figures become about 
3.16 and 5 at 95 pounds, W and 6 at 115, ^\ and 6.4 at 135, 
and -gV 3^"d 7 when the pressure becomes 155 absolute, cr 
140 pounds by gauge. 

This gradual shifting of the ratio of expansion giving 



24° 



STEAM ENGINES FOR 



PERFORMANCE OF 

WITH 







u 

V 


V 






V 


V 


6 


e 
.0 




0. 
■a 


■3 


a 







3 o- 


3 O- 


3 
S 

V 


a 






< 

1) 

3 


V 

in 
'0 




is. 




0. 
B 

V 



.0 




3 


S3 


a 
S 

V 


d 


C 3 

V 


H T3 

5 = 
S y 


c c „• 

■330 
Coo 


H 
c 

1 

V 


« 


u 


CU 


H 


a 


J 


H 


h 


H 


16 


I-I6 


75 


768.6 


.175622 


110,437 


3.22 


463-7 


605.4 


8 


\i 


75 


768.6 


. 175622 


110,437 


7.08 


1,020 


638.6 


4 


y\ 


75 


768. 6 


.175622 


110.437 


15-55 


2,239 


676.0 


2.7 


% 


75 


768.6 


.175622 


"o,437 


24.29 


3,498 


699.7 


3 


^ 


75 


768.6 


.175622 


110,437 


34.15 


4,918 


719.0 


1.6 


% 


75 


768.6 


.175622 


110,437 


44.00 


6,336 


734.2 


16 


1-16 


95 


785.1 


.219430 


151,336 


4.08 


588 


615.0 


8 


j^ 


95 


785-1 


.2T9430 


151,336 


8.97 


1,292 


649.4 


4 


34 


95 


785.1 


.219430 


151,336 


19.70 


2,837 


688.4 


2.7 


% 


95 


785.1 


.219430 


151,336 


30-77 


4,431 


713.0 


2 


^ 


95 


785.1 


.219430 


151,336 


43-26 


6,229 


733.1 


1.6 


^ 


95 


785.1 


.219430 


151,336 


55-72 


8,024 


749-0 


16 


1-16 


"5 


799.1 


.262732 


179,142 


4-94 


711. 8 


623.0 


8 


^ 


"5 


799.1 


.262732 


179.142 


10.86 


1,564 


658.4 


4 


^ 


115 


799.1 


.262732 


179,142 


23.S4 


3,433 


698.6 


2.7 


% 


"5 


799.1 


.262732 


179,142 


37-25 


5,364 


724.0 


2 


j^ 


"5 


799.1 


.262732 


179,142 


52.36 


7.540 


745 


1.6 


% 


"5 


799.1 


.262732 


179,142 


67.46 


9,714 


761.5 


16 


1-16 


135 


811. 2 


.305659 


206,386 


5.80 


835.6 


630.0 


8 


j^ 


135 


811. 2 


.305659 


206,286 


'2.75 


1,836 


666.2 


4 


^ 


135 


811. 2 


.305659 


206,286 


27.99 


4,031 


707.6 


2.7 


% 


135 


811. 2 


.305659 


206,286 


43.73 


6,297 


733-9 


2 


Jr^ 


135 


811. 2 


.305659 


206,286 


61.47 


8,852 


755-3 


1.6 


% 


135 


811. 2 


.305659 


206,286 


79.19 


11,403 


772.4 


16 


I-16 


155 


822 


.348265 


232.738 


6.66 


959.4 


635.80 


8 


Jl 


155 


822 


.348265 


232,738 


14.63 


2,106 


673.0 


4 


M 


15s 


822 


.348265 


232,738 


32.14 


4,628 


715-3 


2.7 


% 


155 


822 


.348265 


232,738 


50.20 


7,223 


742-3 


2 




155 


822 


.348265 


232,738 


70.58 


10,163 


764.5 


1.6 


5^ 


155 


822 


.348265 


232,738 


90.92 


13,092 


782.0 



I. For multiple-expansion engines of similar power these wastes may be divided 
by the number of cylinders in set ies 10 obtain an approximate measure of these 



ELECTRIC LIGHTING PLANTS. 



241 



SMALL HIGH-SPEED ENGINE. 

CONDENSATION. 



u 






Is. 


(A u 

-a ^ 
c a. 
3 


■ss. 


a* . 


eC 


11 





v 


6 . 




s s ° 


m 


PL. 

•a 


1-1 « 


1^ 


CO . 






° M V- 

c 0. 


Q 

u 
u 
0. 


'■3 
c 




c 








a 

10 


3-IOO 


-v--?? 


1.234 


1956 


3-30 


22.86 


38-71 


45-54 


6.42 


/5-J2 


.87287 


i3-37 


1.50 


14-93 


30.23 


35-5S 


11.77 


lb. "J 2 


.61720 


10.32 


.847 


IT. 167 


27.887 


32 -So 


14.97 


18.48 


.50710 


9.88 


.666 


10.546 


30.026 


35-32 


17-85 


21.44 


.43650 


9.71 


-555 


10.265 


32 51 


38.24 


19.90 


24.76 


.3900 


9.66 


.502 


10.162 


34-92 


41.08 


4.83 


12.74 


1.234 


15-73 


1.663 


17-393 


30.133 


35-45 


9-31 


13.21 


.B7287 


11-53 


.969 


12.499 


25-71 


30.24 


15-97 


IS. 42 


.61720 


9.09 


.666 


9.656 


23.076 


29 50 


20.58 


17.72 


.50710 


8.99 


.428 


9.418 


27.14 


31-93 


24.20 


20.34 


.43650 


8.88 


-375 


9-255 


29-595 


34-81 


26.62 


23.11 


.3900 


9.02 


.333 


9-353 


32.46 


38. iq 


6.18 


ii.gi 


1-234 


14.70 


1.360 


16.060 


27.97 


32-91 


11.62 


12.63 


.87287. 


11.07 


• 755 


11.825 


24-55 


28.82 


19.68 


14-97 


.61720 


9-24 


• 415 


9-655 


26.48 


28.97 


25.28 


I7-3S 


.50710 


8.80 


-331 


9- 131 


28.836 


31-15 


29.64 


IQ.88 


.43650 


8.68 


.276 


8.956 


30.00 


33 92 


32.60 


22. 60 


.3900 


8.82 


-25^ 


9.071 


31 -bb 


37-26 


7-534 


II. 3S 


1-234 


14.05 


1.043 


15-093 


26.473 


31-H 


13-91 


12.32 


.87287 


10.75 


.504 


II. 314 


23-63 


27.80 


23-37 


14.67 


.61720 


9-05 


.344 


9-394 


24.06 


28.30 


30.00 


ib.g6 


.50710 


8.60 


.263 


8.863 


25-82 


30.37 


35.00 


19-54 


.43650 


8-53 


■ 236 


8.756 


28. 2q 


SS-28 


38.50 


22.23 


.3900 


8.68 


.208 


8.888 


3' -13 


36.62 


8.89 


10. qS 


1-234 


13-55 


.836 


14-336 


25.36 


28.84 


16.20 


12.03 


.87287 


10.52 


.462 


10.982 


23-03 


27.OQ 


27.00 


14.41 


.61020 


8.89 


■274 


9.164 


23-57 


27-73 


.34-58 


16.72 


.50710 


8.48 


.213 


8.693 


25-41 


2q.8q 


40.50 


ig.28 


•43650 


S.41 


.182 


8.592 


27.87 


32.74 


44.48 


21-95 


.3900 


8.57 


.164 


8-344 


30.68 


36.26 



losses in such engines. It will be noted that the back-pressure and, consequently, 
lost work during the exhaust, are here made somewhat high. 



2 42 STEAM ENGINES EOR 

highest economy of fuel and of steam is better illustrated 
in the last set of curves, in which two exhibit the variation 
of this point of cut-off with varying pressures, while the 
other pair show the progressive gain in economy of fuel and 
of steam in a similar manner ; the numerical values of the 
former quantities increasing, and the latter decreasing, with 
rising steam-pressure. The weight of steam consumed is 
not far, at best, from 

W ~- 2^o/,Vp 

pounds of steam per hour per indicated horse-power when 
working under best conditions, and the best ratio of expan- 
sion, on the same basis, is about 

r = o.^yp. 

The conditions here assumed may be taken as fairly rep- 
resentative of good practice with such an engine in moder- 
ate sizes. Where leakage occurs or when compression is in- 
complete and the clearances thus become sources of addi- 
tional wastes, these figures may be much exceeded. Larger 
engines will be less subject to waste, and the margin be- 
tween the ideal case and the actual may be thus reduced 
approximately in proportion to increasing size of engine. 

The economically desirable ratio of expansion and point 
of cut-off, however, are always somewhat less than are found 
to give lowest expenditure of steam and fuel, since every 
item of cost in the construction of the engine involves a 
corresponding annual charge thereafter, and a compromise 



ELECTRIC LIGHTING PLANTS. 243 

between increasing annual expense on this count and de- 
creasing cost of fuel must be made to secure the best 
results. 

The commercially desirable ratio of expansion is always 
less than that giving maximum duty ; but the margin be- 
tween the two depends greatly upon he relative costs of 
construction and of operation of engine and boiler and cost 
of fuel. Methods of exact computation are becoming devel- 
oped and approximate methods are well known. ^ In gen- 
eral, at the commercial centers the ratio to be adopted in 
designing will not be far from two-thirds that here found to 
give best effect for the ideal case, twenty per cent lower 
than is shown on the diagrams for the actual case, and still 
lower where it is sought to make the most out of an engine 
already set and in operation. 

The distribution of energy supplied the steam-engine 
is easily stated in a general way ; but the exact distribution 
into utilized power and wasted energies is not always read- 
ily ascertainable, even with modern facilities for their meas- 
urement. Assuming this analysis to have been effected in 
any given case, as for a modern " high-speed" engine of 
moderate power and working with high steam-pressure, 
some such balance-sheet as the following would be obtain- 
able. Should the columns fail to balance, it would indicate 
either that a false measurement had been made, that the 
errors of careful observation, even, were sensible and per- 
haps cumulative, or that some source of waste had escaped 
observation altogether, as often did, in fact, the internal 

I. Manual of Steam Engine, Vol. I. Chap. VII. 



244 STEAM ENGINES FOR 

thermal wastes during the greater part of the history of 
the machine and up to within a few years. 

BALANCE-SHEET OF HIGH-SPEED ENGINE. 

RECEIVED. EXPENDED. 

Per Cent. Per Cent. 

Energy stored in steam pro- Utilized by conversion into 

duced in the boiler and dynamic energy at the 

transferred to the en- engine 

gine ICG Wasted by friction 



Total ICO Indicated power . 

External thermal waste 
Thermodynamic wastes 
Internal thermal waste . 



Total 



ID 

2 
60 

28 



In the figure let the ordinates of the various curves be 
made proportional to the weights of steam employed per 
horse-power and per hour under the conditions assumed in 
the construction' of each of the several curves, and let the 
abscissae measure the simultaneous values of the ratios of 
expansion in the given engine, and with the initial and 
back pressures as here assumed — 120 and 3 pounds, re- 
spectively, above vacuum. Compute, first, the quantity 
of steam required for the "ideal case" at each of these 
ratios of expansion, and construct the lower curve of the 
series by passing it through the several computed points. 
Similarly, compute, or find by reference to results of experi- 
ment, the additional and total quantities demanded for the 
engine when the wastes due friction are taken into account, 
and thus obtain the second curve. Next add the weights 
of steam required to supply the heat wasted externally by 



ELECTRIC LIGHTING PLANTS. 245 

conduction and radiation, and, as a final determination, find 
the internal wastes by the action of the cylinder-walls, thus 
ascertaining the locus of the upper limiting curve of the 
series. 

The lower line is obtained by the method of Rankine, 
and accurately represents the efficiencies and the costs of 
power for the ideal representative case taken. It is seen 
that the steam expended varies from about 40 pounds per 
horse-power and per hour at full stroke to 20 at 3.5 expan- 
sions, to 16 at a ratio of expansion of 5, to 12 at 12 expan- 
sions, and to about 10 pounds at a ratio of 20. The gain 
continues indefinitely, but at a decreasing rate, until a ratio of 
about 40 brings us to the limit at which the expansion-line 
begins to fall below the back-pressure line. Were there no 
wastes of extra thermodynamic character, this would be 
the method of operation of the engine which would insure 
highest efficiency and highest " duty." The friction loss 
in the case here taken costs a quantity of steam which is 
decreased with the enhanced efficiencies of higher expan- 
sions, is but little affected by changing loads and power, 
and which, as a percentage of ideal costs, increases con- 
stantly with increasing expansion and decreasing power. 
It is thus found to place a limit to gain, as here taken, at 
about twenty-five expansions and adds, throughout the 
whole range, not far from three pounds of steam per hour 
and per horse-power to the costs of useful work. External 
heat wastes still further exaggerate costs and restrict the 
profitable expansive action of the engine, and a ratio of 
20 is found on the curve to be as much as can be em- 
ployed to advantage when all these wastes are taken into 



246 STEAM ENGINES FOR 

account. Finally, taking up the internal heat wastes by- 
action of the metallic surfaces enclosing the fluid, and as- 
suming, as here, that the engine is of such size and char- 
acter as to waste, in spite of jacket-action, from twenty per 
cent at full stroke to fifty per cent at seven expansions, 
and still higher proportions at greater ratios, the propor- 
tions found actually wasted in, for example, the Sandy 
Hook experiments reported by the writer to the A. S. M. E. 
some years ago, it is found that a maximum efficiency is 
attained, as shown on the upper line, at about seven expan- 
sions, or at the point experimentally found for a more 
efficient engine, operated at a lower pressure, by Hirn and 
Hallauer. This is probably as large a loss, and gives as 
radical an illustration of the facts of such cases, as can be 
fairly expected. 

Whatever the form or dimensions of the engine, such 
construction of its several elements of efficiency as is here 
exemplified will exhibit the facts in which the designer is 
most interested, and show the costs of power and the most 
economical adjustment for high duty. All the thermo- 
dynamic and all the thermal and all the dynamic elements 
are here brought into view, and all measures are taken by a 
common and intelligible scale. 

Every essential element of economical operation being 
thus capable of representation on a common scale, the con- 
struction of such a diagram as is here illustrated and de- 
scribed for each permits the selection of the machine likely, 
on the whole, to prove best ; and we are thus enabled to 
identify the best adjustment of each and to make the com- 
parison of a pair or of a series of available designs under 



ELECTRIC LIGHTING PLANTS. 247 

their several individually best conditions of working. Ad- 
hering to the case thus far studied, that of the simple 
engine, it may be required to ascertain which of a number 
of machines of stated and required power, but differing in 
proportions of stroke and diameter of cylinder, or in speed 
of piston and of rotation, or' even simply in clearance, is 
most desirable. The construction, on a common scale, of 
a set of these diagrams will reveal to the eye and at a 
glance the probably best design. The loss by clearance is 
treated precisely like the wastes by external loss of heat or 
by internal condensation or leakage, and all may, as in fact 
illustrated above, be taken as a common internal waste 
since it often happens, as here, that they cannot well be 
separated with exactness. The best practical method of 
making the comparison is perhaps that of making the dia- 
grams on tracing-paper or cloth and superposing them, one 
upon the other, in pairs, eliminating, one after another, the 
least desirable cases- 
Compound or " Multiple-expansion " Engines afford the 
most interesting and probably the most useful applications 
of such methods of graphical representation of problems of 
this sort. In such comparisons as have been just referred 
to, when multiple expansion, series expansion — or cascade 
expansion, as French writers sometimes call it — is to be 
considered, it becomes especially important to ascertain 
not only what relations of efficiency exist at the best ad- 
justment of each, but often even more important to deter- 
mine the method of variation of efficiencies with varying 
expansion, and the relative values of each type throughout 
their respective as well as their common ranges of working. 



STEAM ENGINES FOR , 



This process of complete study, which, ordinarily is most 
laborious and troublesome — when, especially, their respec- 
tive best conditions of operation are to be identified and 
compared — becomes easy, interesting, and exact when the 
graphical process can be accurately carried into effect. It 
then becomes as easy to discover the best ratios of expan- 
sion, and the ranges of working throughout which the 
simple engine is inferior or the more complex structure is 
superior, as to find absolute values for specified single 
cases. But it is in the exhibition of the relative values of 
the several multiple-cylinder engines that this process is 
perhaps likely to prove of most service and to best illus- 
trate the essential principles involved. 

In the action of the multiple-expansion systems the 
several lines of our diagram become altered in location, 
although retaining their distinctive forms. The ideal case 
only remains unaffected, the thermodynamic conditions 
being the same. The friction-line is usually, but not 
always or necessarily, raised ; the friction of the machine 
being in some cases substantially unaltered, and in others 
even reduced, by modifications of designs introduced by 
" compounding." In the " tandem-compound " engine this 
change is often insensible or unimportant ; in the three- 
crank compound this dynamic waste may be even reduced 
by the balance secured about the shaft-line. The external 
thermal wastes may be but slightly affected also, the reduc- 
tion of the mean temperature of the external surfaces of 
the cylinders compensating roughly the extension of area. 

The internal heat wastes are most remarkably modified 
in good examples of such engines. The upper line of our 



ELECTRIC LIGHTING PLANTS. 249 

diagram is brought down considerably and often very far 
below that location given it in the case of the companion 
simple engine. These wastes may be reduced from six or 
eight pounds, for example, to three or four in the com- 
pound, to two or three in the triple-expansion, or to even 
less weight of steam per horse-power and per hour in the 
more complicated forms of engine, for similar total ratios 
of expansion. The restricted expansion in each of the cyl- 
inders and the reduced area of actively wasteful cylinder- 
wall make the condensation of the entering steam much 
less than at the point of cut-off in the simple engine, and 
the steam thus condensed, being re-evaporated completely 
at its exit, enters the second cylinder in series as steam 
once more, is there again subjected to similar condensation, 
and thus goes on through the series, however extensive, the 
waste from the one cylinder more or less completely meet- 
ing the demand for wastes in the next, and thus approxi- 
mately reducing the total w^aste from this action to that 
comparatively small fraction of the steam supplied from the 
boiler which is represented by the comparatively small con- 
densation in a single cylinder of the series. Every step 
thus gained in the reduction of these internal thermal 
wastes permits corresponding advance to be made toward 
full utilization of the thermodynamic gain due expansion 
and raises the ratio of expansion for best effect. Following 
experience with the most successful designs of mill-engines, 
and comparing cases in which the double-expansion engine 
reduces the internal wastes to one-half, the triple to one- 
third, and the quadruple to nearly one-fourth the magni- 
tudes distinguishing our simple machine, we obtain the 



250 



STEAM ENGINES FOR 



^s rf^ o CO 



LBS. STEAM PER H.P. PER HOUR=2.5 FOR E^l. 

\± tt '^ >-^ >-^ \S. '■! la M CO ife »fi- If 



X ^ 













































^-•^ 


^ 


^ 


^ 


^ 


^^^ 














/ 


^ 


% 


^l^''' 

// 


^ ^ 


















/ 


^ 




// 


/ 






















// 


X/ 


/ 




















/ 


11 


// 


/ / 


/ 




















/ 




' 1 


/ / 






















/ 


, 


/ 




















CO 






1 








1 




















/ 






1 
















hJ 




































-? 




















io 










^4 


















1-1 






r > 


m C 




'■% 


%\ 


















T 3 


8 5 

H 1 


. \ 




T' 


V 





















H 



r 

3 ^ 


1 


s 
\c 
















I-" 




z 


H 



m c 


i| 






Is 












^ 







> 


> 


2 z 
z rn 






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m 

3) 


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> 




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1 


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P,=120; P3=3 LBS. CLEARANCE NEGLECTED; NO COMPRESSION. 



ELECTRIC LIGHTING PLANTS. 251 



three curves in the figure, page 250, lying between the upper 
line already obtained and the lower three lines of the di- 
agram as first traced. 

In each case we find the internal heat wastes constituting 
a heavy tax upon the operation of the engine ; in each they 
become a larger proportion of total expenditures as the 
ratio of expansion becomes greater ; in each case the point 
of minimum expenditure and the ordinate of maximum 
efficiency recede further from the best ordinate for the sim- 
ple machine as these losses become less ; and, as already 
remarked, the ratio of expansion for highest total effect 
becomes a gauge of the value of the type of engine studied. 
While the simple engine did its best work at a ratio of 7 — 
all these machines are assumed to be jacketed — the com- 
pound raises the figure to 10, the triple-expansion to 12 or 
13, and the quadruple-expansion engine does its best duty 
at a ratio not far from 18. With larger and faster engines 
these values of the ratio of maximum effect will be found 
still more distributed and will assume still higher values ; 
but 7 or 8, 10 to 12, 13 to 15, and 18 to 20 are probable fair 
maxima, respectively, in modern good practice with the 
assumed pressure, for the several types of machine above 
taken. 

Comparing the range of competitive operation, it is seen 
that in these particular cases the compound competes 
with the simple throughout the range from the ratio 4 to 
some point beyond our maximum limit on the diagram ; that 
the triple-expansion competes with the compound from 
^ = 5-5» and with the simple between 3.5 and the maximum; 
and that the quadruple similarly competes with the simple 



STEAM ENGINES FOR 



between 3 and the limit, with the triple between 5 and the 
extreme, and with the compound between 3.75 and 20 or 
more. It is assumed in each comparison that the basis of 
the competition is the duty, or the steam required per horse- 
power per hour. The simple engine competes, at its best 
ratio, with the compound and other engines only when the 
latter are working at abnormally low ratios of expansion, 
and each multiple-cylinder machine shows superiority over 
the preceding in our list at expansions which are always 
less than the best ratios of the simpler engine. These 
comparisons, however, obviously may result very differently 
when the complication introduced with the multiple-cylinder 
engine throws up the lines representing friction and exter- 
nal wastes to such height as to make the loss of energy in 
these directions exceed the gain by reduced internal wastes, 
and thus carries the upper line of the representative dia- 
gram for the latter above the line of total cost for the sim- 
pler machine with which it is compared. Very different 
and often very disappointing and unexpected results may 
thus follow where the engines are not suitably adapted to 
their working conditions, or when they are unskilfully de- 
signed and proportioned. 

In all cases, whatever the type of engine, it is likely to 
be found that the beet results are only to be secured when 
the extra thermodynamic wastes of the machine are intel- 
ligently treated and made as small as practicable. It is in 
this direction that the indications are that the greatest 
advances are to be made in the immediate future of the 
history of the steam-engine. 



ELECTRIC LIGHTING PLANTS. 



253 







i\\ 




















40 


























m\ 


^ 












^-^--^^ 


^ 








^^ 






iNTEf 


^JmT^^ 


^^St^ 


^^ 






30 












^ 


^ 






SAME- COM PO 


IND. 

F. 








• — £SSl 


RNAL HFax-WAS.T 












u FRIKTlnN-wlSTF. 


















20 


































10 








































































1 






J 




J 




i 




) 


6 



HIGH-SPEED, SINGLE VALVE ENGINE. 
SIMPLE ENGINE UNJACKETED. COMPOUND ENGINE JACKETED. 

Steam at/i = 120 lbs. absolute ; pz = 20. 



Specific Applications of the principles illustrated in the 
general case just presented will be easily effected where the 
data are available. For example, let the preceding figure 
represent the distribution of useful energies and wastes in 
the case of a high-speed engine with single valve. The 
thermodynamic case is computed as per Rankine and as 
in the earlier work of the author.^ The steam-consumption 
is found by experiment to be approximately measured by 
w = 45/Vr. This quantity is increased, when the friction 

I. Rankine, p. 192 ei seq.; Thurston's Manual, VoL I. Arts. 116, 117, and especially 
123, 137. 



2 54 STEAN ENGINES FOR 

of the engine is taken into account, by about ten per cent 
at ordinary expansions, and the external heat wastes add a 
very nearly equal amount, both these wastes, however, being 
found by experience to be variable slightly with varying 
power and to be somewhat less as an absolute amount and 
greater relatively with decreasing expansion. Friction is 
taken as six per cent of the full power at full stroke, heat 
waste as 0.5 B. T. U. per square foot per hour per de- 
gree difference of temperature between the internal and the 
external temperatures. Adding the internal wastes by con- 
densation, leakage, clearance, and wire-drawing, following 
Clark for the first-mentioned up to the middle of our range 
and later practice beyond, we obtain the upper curve and 
find our profitable expansion restricted to about r= 2,5 ; 
which accords with general experience from Clark's earliest 
work to the present time. But should these last wastes be 
decreased by compounding or superheating, as is known to 
be practicable, to one-half their present amount, the limit- 
curve would fall to the second line, and the allowable ratio 
of expansion for highest duty and lowest consumption of 
fuel in regular work would fall correspondingly, giving a 
higher ratio r = 4 or 5, and a consumption of fuel or of 
steam more nearly 3 than 4, and 25 than 32, as the first 
set of figures would probably read. In other words, the 
gain would be not far from twenty-five per cent. Both the 
first and last results have been bettered by engines of each 
type ; but the relative standing of the two should be very 
much as here indicated. 

Financial Conditions, as was shown by Rankine as early 
as the middle of the nineteenth century, are the final limit- 



ELECTRIC LIGHriNG PLANTS. 255 

ing considerations in adjusting the power of an engine and 
its method of expansion to secure the best possible results 
in any given location and in stated conditions of the market 
for labor and material. 

It is easy to see that if the vertical scale of our diagrams 
were, as it might perfectly well be made, one of dollars in- 
stead of weight of steam we might superpose upon the 
series of curves constituting each another, which should 
represent the varying costs of power external to the engine- 
and the boiler-plant, those costs which measure the annual 
value of capital invested and expenses incurred, apart from 
the internal costs of production of the power, — such as, for 
example, in the former class, the interest on costs of engine, 
boiler, buildings, etc., — and on the same scale which would 
measure the costs of the steam-supply already treated of. 
Referring to the first set of curves, assume the next to the 
upper line to represent these " internal " costs and the upper 
curve to measure the " external " expenses, it is here seen 
that, as is the known fact, the latter being an increasing 
relative magnitude, the departure of the pair of curves from 
each other with increasing expansion indicates that these 
new considerations dictate still further restriction of the 
ratio of expansion and still further narrow the range of 
nearly constant economy. As is elsewhere shown by the 
author, this restriction is often more effective than even the 
enormous influence of internal wastes has been seen to 
prove. Where the designer seeks to ascertain what adjust- 
ment will give him the best work in proportioning an engine 
of either class to perform a specified amount of work, he 
often finds it necessary to adopt a ratio of expansion not 



256 STEAM ENGINES FOR 

exceeding two-thirds that dictated by the solution of the • 
problem above studied.' 

Performance under Test, as illustrated in the trial of 
this class of engine, may be gauged by the following data and 
results of an engine-trial made in the usual manner, the 
engine being of 15 to 20 horse-power, compound and con- 
densing, and of the dimensions given below. With larger, 
faster, or better designed, and especially better protected, 
engines wastes may be reduced somewhat below those 
stated, and correspondingly nearer approximations effected 
to the goal sought by the engineer in designing economical 
engines — i.e., to the performance of the ideal machine." 



DIMENSIONS OF ENGINE. 

Diameter of high-pressure cylinder 12 in. 

Diameter of low-pressure cylinder 20 " 

Length of stroke (nominal) 14 " 

Length of stroke (measured) 13-97 in. 

Length of stroke (measured) 1. 164 ft. 

Diameter of piston-rod 1-9375 in. 

Area of high-pressure piston, head 113.098 sq. in. 

Area of high-pressure piston, crank no. 149 sq. in. 

Area of low-pressure piston, head 311. 211 " 

Area of low-pressure piston, crank 311. 211 " 

Piston displacement, high-pressure, head 91425 cu. ft. 

Piston displacement, high-pressure, crank 89042 " 

Piston displacement, low-pressure, head 2.51575 " 

Piston displacement, low-pressure, crank 2.51575 " 

Clearance, high-pressure cylinder, head I57i6 " 

Clearance, high-pressure cylinder, crank 14718 " 

Clearance, low-pressure cylinder, head 31422 " 

Clearance, low-pressure cylinder, crank 31925 " 

1. Manual of the Steam Engine, Vol. I. Chap. VII. 

2. Thurston's Manual of the Steam Engine, Vol. I. p. 398, and Chap. V. § 129-131. 



ELECTKIC LIGHTING PLANTS. 257 

Clearance, per cent of stroke, high-pressure cyl- 
inder, head I7-50 

Clearance, per cent of stroke, high-pressure cyl- 
inder, crank 16.20 

Clearance, per cent of stroke, low-pressure cylin- 
der, head 7-40 

Clearance, per cent of stroke, low-pressure cylin- 
der, crank 7.60 

Volume of receiver-space. ; 1.1455 cu. ft. 

Volume of space in pressure-plate 12819 " " 

Volume of space in pressure-plate, per cent of 

stroke 5.09 

The engine is a " tandem compound." The computa- 
tions of probable wastes, on the assumed basis previously 
taken, of correspondence with those of the Sandy Hook 
experiments, would give figures, reduced to expenditures 
per horse-power and per hour, as on page 258, about one- 
half those of the smaller engine referred to on page 238,* 
and would, with ten per cent friction, be as follows : 

At the lowest pressure, 75 pounds, maximum economy 
of steam and fuel is found at a cut-off very near •j'j, or a 
ratio of expansion of about 4.5, when the dynamometric 
power is taken, or at about a cut-off of 0.2 and r = 5 on the 
basis of indicated power. These figures become about 3.16 
and 5 at 95 pounds, \\ and 6 at 115, -^^ and 6.4 at 135, 
and yV ^'^d 7 when the pressure is 155 absolute, or 140 
pounds by gauge. 

The wastes average four or five pounds. The details 
of the machine need not be here given. ^ It is only neces- 
sary to say that the machine is carefully balanced, has good 



1. See Manual, Chaps. V.-VI. 

2. For details see Manual of the Steam Engine, Vol. I. Art. 35, p. 142. 



258 



STEAM ENGINES FOR 



EFFICIENCIES OF HIGH-SPEED ENGINE. 





















u 




nn ^ 


Ph 


rt 








a 


c a 


c ■ 

.sill 


S 






■a 


a-" 






^ 6 





3 


S3 




affi 


c a 
C^ ri 


0. OJ 
(D.S 


)^ 


u 


c 


in 


^H 


H 


1/2 


16 


I-I6 


75 


J5-SS 


11.5 


27-35 


30.6 


8 


^ 


75 


'5-32 


7-5 


22.82 


25-4 


4 


i4 


75 


lb, 7 2 


5-5 


22.22 


2b.7 


2,7 


^A 


75 


18.4S 


5-3 


23-78 


2b. 4 


2 


M 


75 


21.44 


5-3 


2b. 7 4 


29-7 


1.6 


% 


75 


24.7b 


5-2 


2q qb 


33-3 


16 


1-16 


95 


12.74 


8.7 


21.44 


23.8 


8 


^ 


95 


13.21 


6.2 


19-41 


21. b 


4 


Va 


95 


13-43 


4.8 


20.2b 


22.5 


2.7 


■ % 


95 


17.72 


4-7 


21 42 


22.7 


2 


\^ 


95 


20.34 


4.6 


24 14 


27.0 


1.6 


% 


95 


23-11 


4.6 


27.71 


30.8 


16 


i-i6 


115 


II .QI 


8.0 


19.91 


22.1 


8 


Vs 


"5 


i2.bS 


5-9 


18.58 


20.b 


4 


H 


>I5 


14-97 


4.8 


iq.77 


22.0 


2.7 


% 


"5 


1735 


4.6 


21-95 


24.4 


2 




lis 


1Q.88 


4-5 


24.38 


27.1 


1.6 


% 


"5 


22 -.bo 


4.0 


2b. bo 


29.9 


16 


I-I6 


135 


11.38 


7-'; 


18.88 


21 .0 


8 


Va 


135 


12-32 


5-6 


17. q2 


iq q 


4 


Va 


135 


14.67 


4-7 


19-37 


21-5 


2.7 


% 


135 


ib.qb 


4.4 


21 :3b 


23-7 


2 


^ 


13s 


iQ-54 


4.4 


23-94 


2b. s 


1.6 


% 


'35 


22.23 


4.4 


2b. bs 


2q.b 


16 


1-16 


155 


10. q8 


7-1 


18 08 


20. 1 


8 


1^ 


155 


1 2. OS 


5-5 


17.55 


^9-5 


4 


M 


155 


14.41 


4.6 


iq.oi 


21.0 


2.7 


% 


155 


lb. 7 2 


4.4 


2 1. J 2 


21. 1 






155 


iq.28 


4-3 


23-58 


25-1 


1.6 


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155 


21-95 


4.1 


2b. OS 


28. g 



ELECTRIC LIGHTING PLANTS. 259 

provisions for free lubrication, and in the only case in 
which the writer has had extended experience with it ^ has 
shown itself an excellent example of its class. 
The following are the results of trial : 

DATA AND RESULTS. 

Time of starting 6.45 p.m. 

Time of stopping ir.45 " 

Duration of trial 5 hours. 

Total number of revolutions (per continuous 

counter) 60300 

Revolutions per minute 201 

Barometer in inches of mercury 29.40 

Atmospheric pressure 14.50 pounds. 

Boiling-temperature at atmospheric pressure.. 211°. 10 

Boiler-pressure by gauge. 98.00 pounds. 

Boiler-pressure, absolute 112.50 " 

Pressure in steam-chest, low-pressure cylinder 34-00 " 

Vacuum-gauge, inches of mercury 22.99 

Temperature of condensed steam 130°. 8 

Temperature of injection-water 47°.9 

Temperature of discharge-water 106°. 7 

Temperature in calorimeter, steam-pipe 212°. 8 

Quality of steam in steam-pipe 95-50 per cent. 

Quality of steam in compression (assumed). . . . 100.00 " 

Quality of steam in exhaust 93-30 " 

Total weight of condensed steam 11594.50 pounds. 

Pounds of wet steam per stroke, mean .0961.184 

Pounds of wet steam per stroke, head . 103593 

Pounds of wet sieam per stroke, crank .088704 

Cubic feet of condensing-water per minute (by 

meter) 9.304 

Pounds per revolution 3.033 

Pounds per stroke, head 1-634 

I. An engine of this kind was built in the shops of Sibley College, Cornell Univer- 
sity, and has now for several j^ears done good work driving dynamos for experi- 
mental work m the Department of Physics, and later in furnishing power in the 
electric-light and power station. 



26o 



STEAM ENGINES FOR 



Pounds per stroke, crank . = 1-399 

Length of brake arm 8.07 feet. 

Gross weight on brake-scale 367.00 pounds. 

Net weight on brake-scale 323.75 " 

Available delivered horse-power 99-99 

Head. Crank. Total, 

M. E. P., high-pressure cylinder 30.096 26.460 — 

M. E. P., low-pressure cylinder 16.854 13.729 — 

I. H. P., high-pressure cylinder 24.132 20.664 44-796 

I. H. P., low-pressure cylinder.. .... . 37.188 30.294 67.482 

Total I. H. P 112.28 

Total D. H. P 101.17 

Efficiency, per cent 90.16 

Total weight of wet steam 11595.50 pounds. 

Weight of wet steam per hour 2319.10 " 

Weight of dry steam per hour 2234.72 " 

Weight of steam per I. H. P. per hour ig.goj " 

tVeight of steam per D. H. P. per hour ^^-35 " 



HIRN'S ANALYSIS— DATA. 



High-pressure Cylinder. 



End. 



Head. 

Cut-ofif, per cent of stroke 26.40 

Release, per cent of stroke 75-17 

Compression, per cent of stroke.. .... 12.56 

Absolute pressure at cut-off 105.30 

Absolute pressure at release 56.00 

Absolute pressure at compression. . . . 49.00 

Absolute pressure at admission 73.00 

Volume in cubic feet at cut-off .40045 

Volume in cubic feet at release .76313 

Volume in cubic feet at compression... .27210 

Volume in cubic feet at admission.. . . .15716 

External work B.-T. U., admission. . . 4.9000 

External work B. T. U., expansion. .. 5.0681 

External work B. T. U,, exhaust..... 3.4571 

External work B. T. U., compression 1.2419 



C7aiik. 

■ I9-S3 

62.91 

12.56 

104.50 

49.00 

46.00 

81.00 

.32673 

•70351 
.25903 
.14718 
3.5958 
4.8380 

2.5497 
1.2749 



ELECTRIC LIGHTING PLANTS, 



261 



Head. 

External work B. T. U., total 5.2692 

Steam from boilers, pounds 10.3593 

Steam in clearance, pounds 2.6906 

Steam, total, pounds . . . . = 13.0.499 

Heat in exhaust 11373.70 

Heat supplied to engine 12220.95 

Sensible heat at admission 741-45 

Internal heat at admission 2207.16 

Sensible heat at cut-oft 3940.42 

Internal heat at cut-off 7747- 50 

Sensible heat at release 3363.00 

Internal heat at release 8490. 55 

Cylinder loss during admission 2991.64 

Cylinder loss during expansion 672.44 

Cylinder loss during exhaust 2535.37 

Cylinder loss during compression .... 536.51 



Crank. 



4 
8 

277 

II 

9738 

103 1 6 

785 
2264 
3510 
6279 
2901 

6959- 
3216, 

554. 

2737' 

181. 



6092 

8704 

91 

6495 

80 

00 

99 
20 
80 
00 
30 
30 
82 
60 
76 
83 



Low-pressure Cylinder. 



Cut-off, per cent of stroke 

Release, per cent of stroke 

Compression, per cent of stroke 

Absolute pressure at cut-off 

Absolute pressure at release 

Absolute pressure at compression 

Absolute pressure at admission 

Volume in cubic feet at cut-off 

Volume in cubic feet at release. 

Volume in cubic feet at compression.... 

Volume in cubic feet at admission 

Volume in cubic feet of space in pres- 
sure-plate 

External work B. T. U., admission., .. 
External work B. T. U., expansion.... 

External work B. T. U., exhaust 

External work B. T. U., compression.. 

Total 

Steam from boiler, pounds 



36.18 


24.48 


88.23 


87.72 


33-82 


22.80 


25.50 


26.50 


12.00 


9.70 


3.00 


3.00 


22.00 


19.00 


1.2209 


.92491 


2.3974 


2.3752 


1.0359 


-76953 


.3142 


.3192 


.12819 


.12819 


5-4233 


3-5390 


4.1360 


4.3582 


.4109 


-5811 


1-5339 


•9773 


7.6146 


6.3388 


10.3593 


8.8704 



2 62 STEAM ENGINES FOR 



End. 



Head. Crank. 

Steam-clearance, pounds 1.7418 1-5387 

Steam, total, pounds 12.1011 10.4091 

Heat of condensed steam 1023.50 876.40 

Condensing-water, pounds 108.937 93.279 

Heat given to condensing-water 960S.30 8227.20 

Heat supplied to engine ii373-7o 9738.80 

Sensible heat at admission 35i-5i 298.39 

Internal heat at admission. ... , 1528.00 1362.50 

Sensible heat at cut-off 2599.20 2208.30 

Internal heat at cut-off 6768.20 5324.50 

Sensible heat at release 1980.00 1611.70 

Internal heat at release 6783,50 5694.20 

Total heat in steam at beginning of 

compression 935.66 695.07 

Heat confined in pressure-plate 521.69 465.36 

Cylinder loss during admission 3343.48 3512.99 

Cylinder loss during expansion 331-39 674.28 

Cylinder loss during exhaust 2763.37 2434.66 

Cylinder loss during compression 268.77 402.73 



SUMMARY OF RESULTS. 
High-pressure Cylinder. 

End. 



Head. Crank. 

Per Cent. Per Cent. 

Heat lost by initial condensation 24.48 31.18 

Heat restored during expansion 5.50 5.38 

Heat rejected during exhaust 20.75 28.11 

Heat lost during compression 4.39 1.76 

Heat titilized, work (actual efficiency) 4.31 4.47 

Ther77iodynamic efficiency 8.77 8.77 

Efficiency compared with ideal 49. 10 50.90 

Quality of steam entering (per calorimeter). .. . 95.50 95-50 

Quality of steam at cut-off (computed) 74-19 67.33 

Quality of steam at release (computed) 78.01 71.07 

Quality of steam at admission (assumed) 100.00 100.00 

Quality of steam in exhaust (computed) 104.00 104.00 



ELECTRIC LIGHTING PLANTS. 263 

Low-pressure Cylinder. 

End 



Head Crank. 

Per Cent. Per Cent. 

Heat lost by initial condensation 29.40 36.07 

Heat restored during expansion 2.gi 6.92 

Heat rejected during exhaust 24.30 25.00 

Heat lost during compression 2.36 4.13 

Heat utilized, ivork (actual efBciency). 6.69 6.51 

Tkerviodyna7nic efficiency 1,5.66 15.66 

Efficiency compared with ideal 42. 70 41 . 56 

Quality of steam entering (per calorimeter). .. . 93.30 93.30 

Quality at cut-off (computed) 64.22 50.63 

Quality at release (computed) 64.76 54.00 

Quality at admission (assumed) 100.00 100.00 

Quality of steam in exhaust (computed) 90.12 102.00 

Averaging the given values for the head and crank ends 

for each of the two cylinders, the following values are ob- 
tained : 

Cylinders. 



H.-p. L.-p. 

Per Cent. Per Cent. 

Quality of steam entering (per calorim- 
eter) 95.50 93.30 

Quality of steam at cut-off (computed) . . 70.76 57-42 

Quality of steam at release (computed). . 74.54 59-3S 

Quality of steam at admission (assumed) 100.00 100.00 

Quality of steam in exhaust (computed).. 104.00 96.06 

Heat lost by initial condensation 27.83 32.73 

Heat restored during expansion 5.44 4.51 

Heat rejected during exhaust 24.43 24.65 

Heat lost during compression 3.07 3-24 

Heat utilized, work (actual efficiency) 4.39 6.60 

Total 10. 99 

Thermodynamic efficiency 8.77 15.66 

Total 24.43 

Efficiency coi?ipared with ideal 50.00 42, 13 

Mean 46.07 



264 



STEAM ENGINES FOR 



POWER TABLE— "AUTOMATIC" ENGINE. 

CUTTING OFF STEAM AT i STROKE. 



Size 
of 


Constant. 


Revolu- 
tions 
per 
Minute. 


Initial Steam-pressure. 


Engine. 


50 


60 


70 


80 


90 


100 


7" X 9" 


.00175 


300 
340 


I3-I 
14.8 


15-7 
17.8 


18.3 
20.8 


21.0 
23.8 


23.6 
26.7 


26.2 
29.7 


8" X 9" 


.00229 


300 
340 


17. 1 
19.4 


20.6 
23-3 


24.0 
27-3 


27.4 
3I-I 


3°-9 
35 -o 


34-3 
38.9 


8^" X loi" 


.00302 


270 
310 


20.3 
23-4 


24.4 
82.0 


28. 5 
32.7 


32.6 
37-4 


36.6 
42.1 


40.7 
46.3 


9^" X loj" 


.00376 


270 
310 


25-3 
29.1 


30.4 
34-9 


35-5 
40.7 


40.6 
46.6 


45.6 
52-4 

53-5 
62.1 


50-7 
58.2 


10" X 12" 


. 00476 


250 
290 


29.7 
34'5 


35-7 
41.4 


41-3 
48.3 


47.6 
55-2 


59-5 
69.0 


11" X 12" 


.00576 


250 
290 


36.0 
41.7 


43-2 
So.i 


So-4 
58.4 


57.6 
66.8 


,64.8 
75-1 


72.0 
83-5 


12" X 15" 


.00857 


210 
250 


44.9 
53-5 


53-9 
64.2 


62.9 
74-9 


71.9 
85.7 


80.9 
96.4 


89.9 
107. 1 


13" X 15" 


.01005 


210 

250 


.52.7 
62.8 


63.3 
75-3 


73.8 
87.9 


84.4 
100.5 


95-0 
113. 


105 -S 
125.5 


i4i" X 17" 


.01417 


200 
240 


70.8 
85.0 


85.0 
no2.o 

103 -5 
124.2 


99 I 
119. 


"3-3 
136.0 

138.0 
165.6 


127.5 
IS3-0 


141. 7 
170.0 


16" X 17" 


.01726 


200 
240 


86.3 
103.5 


120.8 
144.9 


155-3 
186.4 


172.6 
207.0 



The "constant" is that quantity which being multiplied 
by the mean effective pressure and the revolutions per 
minute, the product is the horse-power. 



ELECTRIC LIGHTING PLANTS. 



265 



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266 



STEAM ENGINES FOR 



The deductions to be drawn are that the constants as- 
sumed in the tabulated work are substantially correct for 
an engine of this class of good design and construction 
and operated under ordinarily favorable conditions. The 
table of engine efficiencies may therefore be taken as a 
probably safe guide in the design of such engines, assuming 
that correct proportion of volume of cylinders and the best 
ratios of expansion are adopted for the cases to be met. 




r 




~^^, 



^ 






ELECTRIC LIGHTING PLANTS. 267 

VII. 

Direct-Connected Engines ; Stations. 

u pviRECT-CONNECTED ENGINES" have come 
into use since about 1890 in large numbers. With 
the older arrangement of belted connection between the en- 
gine and the dynamo the space occupied was very large and 
the cost of wear and tear of belting very considerable. 
Where land is costly, as in the large cities, and the outlay for 
real estate therefore necessarily heavy at best, it is impor- 
tant to economize in the occupation of ground- and floor- 
space ; and the abandonment of the belt, the placing of the 
dynamo directly beside and in actual contact with the driv- 
ing-engine, is obviously a means of securing immense reduc- 
tion in the volume and cost of the installation. By the adop- 
tion of the multipolar generator it becomes practicable to 
secure any desired speed of rotation, and to adapt the speed 
of engine and of dynamo, the one to the other, in the most 
satisfactory manner. The cost of the generator is somewhat 
increased for a given power ; but since, for a stated output^ 
the quantity of metal employed is not variable to any large 
degree, the difference in this respect, especially for large 
powers, is not enough to influence the solution of the ques- 
tion in any important degree. 

Steam-engines employed for this system of application of 
power are sometimes horizontal, oftener vertical in large 
powers, and may be of any type found useful for any pur- 



268 



STEAM ENGINES FOR 



poses, from the simple upright " semi-portable " style of en- 
gine to the triple- and quadruple- expansion marine type, 
which latter is a favorite with a number of designers and 
engineers. The following are illustrations of such applica- 
tions of the moderate-speed and the high-speed engines. 

As an excellent illustration of the direct-connected en- 
gine the accompanying plate is given — a McEwen engine 
with the generator of Professor Ryan, head of the Depart- 
ment of Electrical Engineering of Sibley College, who was 




" Inertia Governor." 



one of the early designers of this type. The engine is built 
either horizontal or direct, like other forms shown elsewhere. 
The generator has from lo to 20 poles, as speeds of engine 
vary from 500 down to 150 revolutions and power demanded 



ELECTmC LIGHTING PLANTS. 269 

increases from, ordinarily, 10 or 15 to 300 or 400 K. W., 
400 or 500 H. P. 

The engine has the same general form as the high-speed 
engine of the best makers usually, with well-studied details 
and an interesting type of governor, very simple, very effec- 
tive, and very reliable. The action of centrifugal force and 
that of inertia conspire to insure quick, strong, and accu- 
rate movement, while the dash-pot, F, prevents swinging. A 
pivoted and weighted bar, CC, a spring, G^ and the dash- 
pot constitute the whole system. The bearing and its pin 
are fitted with steel rollers and no lubrication is needed. 

The generator here shown is built with Ryan " balancing 
coils " and various details by Mr. Thompson all resulting 
in giving a machine weighing in the sizes just specified from 
about 60 to 80 pounds per K. W., 45 to 60 pounds per H. P., 
and permitting variation of work through wide ranges with- 
out arcing or other difficulty.' 

The cut on page 270 shows a straight-line engine 
connected to a General Electric Company's dynamo. 
Aside from the adjustable outboard pedestal, the base, 
pedestals, and dynamo-supports are cast in one piece, where 
it can be placed if in one piece, and the whole arranged to 
be filled with masonry before setting on foundation. 

The arrangement for connection between engine and 
dynamo includes a safety-coupling betv/een the two. A 
flange is forged on the dynamo-shaft, a cone is keyed and 
pinned on the engine-shaft, and a solid bush is bolted to the 
flanee and drawn on the cone so as to create drivinsr-friction 



I. For details of this interesting construction see the papers of Prof. H, J. Ryan 
and of M. P. Thompson. 



270 



STEAM ENGINES FOR 



enough to run the dynamo, but not so much as to burn it 
out in case of a short circuit. Either dynamo or engine 
can be dismantled without disturbing the other. 




DiRECl-CONNECTED SXRAIGHT-LINE ENGINE. 

Direct-connected engines are often of great size. Thus 
the West End Street Railway Company of Boston have 
two Rice & Sargent cross-compound engines, direct-con- 
nected to electric generators, of which the general dimen- 
sions are as follows : 



CROSS-COMPOUND DIRECT-CONNECTED ENGINES. 

Indicated horse-power, each engine 1,500 

Diameter of high-pressure cylinders 26 in. 

Diameter of low-pressure cylinders 50 in. 



ELECTRIC LIGHTING PLANTS. ^^i 

Length of stroke 60 in. 

Number of revolutions per minute So 

Steam-pressure per square inch 150 lbs. 

Diameter of fly-wheels 24 ft. 

Weight of each fly-wheel 120,000 lbs. 

Diameter of shafts in wheels 24 in. 

Diameter and length of main bearings. ... 22 in. X 38 in. 

The rims of the fly-wheels are composed of forged steel. 
Jet-condensers and air-pumps, driven by independent en- 
gines, are 'ased. Reheating receivers are placed between 
the cylinders, and the piping is arranged so that either 
cylinder of either engine may be ruii alone if desired. 

The Brotherhood type of engine, characterized by its 
equidistant cylinders — three or four- — arranged to connect 
with a common crank and pin, is an example of complete 
balancing, and can be driven, like all such engines, up to 
enormously high speeds. The author has know^n them to 
be carried, experimentally, up to above 2,500 revolutions per 
minute, and 1,000 revolutions has been frequently attained. 
The construction here illustrated is that built in the United 
States by the Chester Co. This form of engine is illus- 
trated in the figure as applied to a standard type of dynamo- 
electric machine. With most forms of even " high-speed " 
engine a low-speed dynamo must be especially designed to 
couple with it ; but this class of engine adapts itself to the 
ordinary speeds of moderate-sized and large dynamos. 

Tower's Spherical Engine, as constructed by Heenan & 
Froude of Manchester, G. B., is shown in the engraving — 
a peculiar and very compact and fast-running machine, 
especially applied to the driving of electrical and other 
rapidly rotating apparatus. It consists of a spherical work- 



272 



STEAM ENGINES FOR 






Hcr..jj«"^> 








ELECTRIC LIGHTING PLANTS. 



273 



ing " cylinder" in which a disk spins, driving its supporting 
shaft at any required speed. These engines are coupled 
direct to the dynamo, or to a fan or pump, and are much 




The Tower Spherical Engine. 

used on shipboard when compactness and noiselessness are 
demanded. This is one of the most singular forms • of 
steam-engine yet successfully introduced. 

The steam-turbine constitutes a class of steam-engine 
which, although the first invented, and familiar as a type 
to all engineers from the days of Hero the Younger, and 
known to have a high theoretical and moderately high actual 
efficiency, has been only experimentally used until a very 
recent date. That of Hero is illustrated in the next figure. 



2 74 



STEAM ENGINES FOR 



The Atwater engine of about 1840 was of this type, and 
was said to be as economical as the engines of the time 
of equal power. Steam-turbines of the inward-fiow type 
have been used by Gorman and others.' 

The later " compound " steam-turbine has recently been 




Hero's Steam Turbine. 

somewhat extensively employed in the operation of dynamo- 
electric machinery. It consists of two sets of parallel-flow 
turbines set, in twin series, on one shaft on either side the 
induction-pipe, thus balancing. The passages are gradually 
enlarged as the volume of the steam increases with its pro- 
gressive expansion. 

The turbines thus alternate with their guide-blades, and 



I. Rankine, p. 538. 



ELECTRIC LIGHTING PLANTS. 275 

both the vanes and the blades are carefully proportioned 
and set to secure maximum attainable efficiency at the pro- 
posed speed of rotation, their pitches and depths being suit- 
ably varied. 

The computed efficiency, without allowances for wastes, 
is about 87 per cent. The actual consumption of steam is 
found to be 35 to 40 pounds per electrical horse-power pro- 
duced and per hour as steam-pressures rise from 60 to 90 
pounds by gauge. The speed of rotation ranges from 5,000 
or 10,000 revolutions per minute upward, according to 
size and steam-pressure, 18,000 and 20,000 being common 
speeds for the smaller sizes. 

Dow's turbine is an inward-fiow wheel with concentric sets 
of guides and vanes in series, and is said to have attained 
35,000 revolutions per minute, working regularly at 25,000, 
consuming 55 pounds of steam per horse-power per hour. 
Only the most perfect construction is here admissible. 

The theory of this type of machine is that familiar to the 
hydraulic engineer, and the speeds of orifice for maximum 
efficiency are well-known to be infinite in the Hero class of 
turbine and approximately one-half the final velocity of flow 
in the guide-blade turbine. Since these speeds are imprac- 
ticable in their use, a certain loss of energy is thus inevita- 
ble. In compensation for this loss, in the steam-turbine, is 
the fact that it is not subject to that fluctuation of tempera- 
ture of parts exposed to contact with the steam which re- 
sults in large wastes by cylinder-condensation in the common 
forms of steam-engine. In this way a gain of from 25 to 
50 per cent, as compared with the latter, is to be counted 
upon. 



276 



STEAM ENGINES FOR 



The Dow turbine, as built for work in connection with 
the Howell torpedo, gives an average of about 11 horse- 
power in coming up to speed in regular working, at, 60 
pounds steam-pressure, and weighs from 100 to 150 pounds, 
or not far from 13 pounds per horse-power.' Its fly-wheel 



=m 



I -^ 







A Sectional View of the Parsons Turbine. 

rim attains a speed of nearly 7 miles an hour at 10,000 
revolutions per minute. The designer estimates its power 
at 150 pounds steam-pressure and the same speed at 40 
horse-power, or one horse-power to 3.75 pounds weight, and 
states that this may be still further reduced to the extraor- 
dinary minimum of 2\ pounds weight per horse-power, a 



I. Electrical World, April i8, i8gi. 



ELECTRIC LIGHTING PLANTS. 277 

figure well within the estimated allowable maximum for use 
in aeronautic work. 

The steam-turbine of Parsons is an engine consisting oif a 
series of turbines, the different pairs of guides and wh&els 
being so placed that the fluid passes successively from orae 
pair to the next. Of the two forms, radial and axial flow, 
only the latter have been used here. Two series of cylin- 
drical turbines are used, arranged symmetrically to the right 
and left of the central steam-inlet, the exhaust taking place 
from the two ends. In this manner a balance is obtained, 
and the bearings are relieved of end-pressure. Oil is forced 
through the bearings by a pump. The bearings are thus 
forcibly deluged with oil, which returns to a rese'rvoir. The 
governor is a suction-fan mounted upon the spindle and con- 
nected with a diaphragm, which operates the throttle-valve 
against the power of a spring. Its action is found to be 
rapid and certain. 

Such engines have been successfully employed in driving 
electric machinery and in "spinning" the "fly" of the 
Howell torpedo. For alternating electric currents this sys- 
tem possesses the peculiar advantage of permitting a " dy- 
namo " to be employed having but two poles. It may be 
readily driven continuously at speeds exceeding 10,000 
revolutions per minute, and, like the Dow turbine, elsewhere 
referred to, has been driven at 20,000 and upward. With 
the lower speeds of revolution usual with ordinary engines 
the number of poles required generally approximates the 
quotient 12,000 divided by the speed of engine, if directly 
connected. 

The best of these machines have demanded from 35 



278 



STEAM ENGINES FOR 




ELECTRIC LIGHTING PLANTS. 279 

pounds of steam per horse-power per hour upward, accord- 
ing to pressure employed. It may be assumed that they 
will require not far from the weight 

V}: 

where p^ lies between 50 and 200 pounds per square inch 
by gauge and the apparatus is operated under favorable 
conditions, the value of a lying between 350 and 400 with 
dry steam. 

In the United States the substitution of the Dow tur- 
bine for the systems previously in use, for torpedoes, has 
brought down the weight and volume of machinery from 
the earlier minimum of 360 pounds and three cubic feet 
per machine to 75 pounds and one cubic foot. 

In this turbine the steam enters through the passage ee 
and finds exit through _///" to the exhaust-pipe g (page 280). 

The main shaft, hh, is carried on journals at each side the 
casing, as seen, and a sleeve, ii, stiffens the central part of 
the shaft and carries the turbine-wheels proper, //, of which 
a pair are used to insure a longitudinal balance of pressures. 
These are " inward-flow " turbines, " compounded " by 
having a number of concentric circles of blades working in 
series, in conjunction with the guide-blades, on cc, as is 
well shown in the next figure. 

Steam entering from ee must pass through the balance- 
disk, k, on the shaft, the spaces on either side and the pas- 
sages nwi to reach the turbine-disk. This keeps the sleeve 
and the three disks automatically adjusted longitudinally 
at the intended very minute distance from the guide-disks, 



STEAM ENGINES FOR 



and insures that contact shall not take place. The sleeve 
is splined to the shaft, and permits slight endwise motion 




of the latter without affecting the action of the turbine. 
The latest development of the steam-turbine in modern 



ELECTRIC LIGHTING PLANTS. 28 1 

work is a modification of the machine of Branca of 1629, 
of which an illustration is given, page 282, as drawn by the 




Dow Turbine. 

inventor.' The turbine of De Laval is constructed on the 
same principle as is, among the water-wheels, that of 
Pelton. In this form of steam-turbine the steam is ex- 
panded from the boiler-pressure to that of the atmosphere 
or, in the case of a condensing engine, to that of the con- 
denser, and its potential energy thus converted into the 

I. History of the Steam-engine, by R. H. Thurston, Fig. 6; N. Y., D. Appleton 
& Co. 



STEAM ENGINES FOR 



kinetic form and with as complete utilization of all stored 
energy, whether that of sensible or of latent heat, as the 
thermodynamic action of the case permits. The issuing 
jet of steam then impinges upon the buckets of the rapidly 
revolving turbine and is thus reversed in direction of flow. 




Barca's Steam-engine a.d. 1629. 

and would be completely deprived of its energy by transfer 
to the machinery were it practicable to drive it up to the 
needed velocity of rotation ; but friction and insufficient 
speed of rotation together waste much of the power stored 
in the outflowing vapor. 

The arrangement of the apparatus is clearly shown in the 
illustration on page 283, and is seen to be precisely that 
of the machine of Branca, with modern refinements in de- 
sign and construction. It is, however, notwithstanding the 
defects of essentially high velocity of rotation and of loss 
by friction and by deflection of the jet of steam from its 



ELECTRIC LIGHTING PLANTS. 



'■83 



proper path, a very remarkably efficient and economical 
form of the steam-engine. Its velocity is from 15,000 to 
25,000 revolutions per minute, according to size and pov/er, 
and this means, of course, its application principally to the 




propulsion of exceptionally high speed machinery, mainly 
to the driving of electric generators, which also must be 
specially designed for its use as a motor. The gearing 



284 S'TEAM ENGINES EOK 



dowrv of the steam-turbine often presents as troublesome a 
problem as the formerly practised gearing up of the older 
and. slow-moving forms of steam-engine. 

The machine is usually geared down from its enormously 
high speed to one-tenth as high velocity at the generator- 
shaft by means of beautifully made helical gearing, and 
the almost impossible task of securing smooth running by 
balancing the rapidly revolving disk of the turbine is 
evaded, more or less perfectly, in the machines built by this 
inventor by the adoption of a long and flexible spindle 
instead of a short and rigid shaft, thus permitting the disk 
to take its own position and to revolve about its natural 
center of revolution. 

Many of these machines have now been installed, par- 
ticularly in Europe, and the reported results of their trials 
have been often very favorable. In some cases their use 
for large " plants " has been adopted, and individual tur- 
bines have been constructed of above 300 horse-power. 

Both forms of turbine have been reported to give a " water- 
rate " of less than 20 pounds per horse-power per hour. 
The Parsons turbine, tested by Professor Ewing, furnished 
100 Board-of-Trade units of energy at a cost of 20 pounds 
of steam per horse-power per hour, equivalent, as estimated, 
to about 15 pounds per I. H. P. with the standard form of 
engine, and fully equal to the best average work of the 
latter class of engine under similar conditions of operation. 
At half-load the water-rate rose to figures one-half higher. 
A De Laval turbine was reported, by its exhibitors at the 
International Exhibition, 1893, to have been tested at the 
University of Stockholm that season, and to have shown a 



ELECTRIC LIGHTING PLANTS. 



285 



water-rate of 8.95 kilogs., 19.7 pounds, per horse-power per 
hour when delivering 63.7 horse-power on the brake. In 
the Parsons wheel the pressure was at entrance 100 pounds 
per square inch, and in the Laval wheel 108 to 122. 




The Ewing trial was conducted with slightly super-heated 
steam, the Laval trial with saturated. In the latter case 



STEAM ENGINES FOR 



the vacuum was 27 inches, in the former somewhat less. 
Turbines of the Branca class, built under the patents 
of De Laval by Breguet of Paris, were supplied to the 
Edison Illuminating Co. of New York with the following 
guarantee : 

'' Each 300-horse-power turbine is to drive two Desroziers 
dynamos, each of 100 kilowatts (133 horse-power) capacity. 
The turbine-shaft is to run at 13,000 revolutions, driving at 
a speed of 1,300 revolutions, by means of helical gearing, 
two dynamo-shafts situated on either side of the turbine- 
shaft. ... If the turbines are built to be operated either 
condensing or non-condensing, as a mongrel type, with a 
steam-pressure of 10 kilos per square centimeter (142 
pounds per square inch) at the throttle, and with a vacuum 
of 65 centimeters at the condenser, the steam-consumption 
per brake-horse-power is guaranteed not to exceed 8|- kilos 
(18.7 pounds) ; with a free exhaust the steam-consumption 
is not to exceed 16 kilos (35.2 pounds). 

*' If it should be contemplated to operate the turbines 
ordinarily with a condenser, the guaranteed steam-con- 
sumption will be reduced to 7^ kilos (16.5 pounds) per 
brake horse-power. In this case the turbine-disk would 
have a diameter of 0.75 meter (29 inches), instead of 0.50 
meter (19I inches) for the mongrel type." 

Light- and power-stations have come to be the most 
numerous and extensive of all sources of mechanical energy 
derived by thermodynamic transformation from the heat- 
energy of §team and of fuel. Hundreds of millions of dol- 
lars have been invested in the United States alone in elec- 
trical transmission of energy from economically located and 



ELECTRIC LIGHTING PLANTS. 287 

arranged steam-engine and boiler " plants." Some estab- 
lishments for power-production are situated in the midst of 
great cities and supply the surrounding districts with elec- 
tric lights ; others furnish the power for operation of hun- 
dreds of miles of electric railways ; still others, placed where 
the sum total of their costs of operation and maintenance 
shall be, as nearly as can be reckoned, a minimum, between 
cities or on lines connecting cities with suburban villages, give 
out energy in always sufficient quantity to meet the enor- 
mously varying demands of lighting or of power lines, or 
both combined ; still others, again, are placed at the great 
waterfalls of the country and, substituting the water-wheel 
for the steam-engine, gather up the floating energy of the 
flowing stream and convert it into electrical form for trans- 
mission five, ten, twenty, a hundred miles, to the point at 
which it is called for, to be employed, untransformed, in 
lighting, or transmuted into mechanical energy to drive 
motors and machinery of all kinds.' 

The development of electric systems of distribution of 
power and light commenced about 1875 with the operations 
of Farmer, of Brush, and of Thomson and Houston. In the 
earlier days the "units " adopted were small, and the gen- 
erators were rarely above 150 kilowatts capacity. All the 
work was performed by means of the then only familiar type 
of machine ; the bipolar generator, and the alternating cur- 
rent, with its wonderful possibilities, were unappreciated by 
the most prominent builders and electricians. The latter 

I. In the following discussion we h^ve drawn upon the published papers of Mr. C. J. 
Field most freely, and on lectures delivered before Sibley College at Cornell Univer- 
sity. We are under obligations to the courtesy of the publishers and editors of Cas- 
sier's Magazine for the illustrations included in this part of the discussion. 



288 STEAM ENGINES FOR 

field was only opened in a practical manner ten years later. 
No experience and little knowledge guided the engineers of 
the time in their designs of machinery or in the arrange- 
ment of their stations. The results on the economy of cur- 
rent-supply and utilization of the extreme irregularity of 
demand for power and for light were understood by few, 
and even fewer saw what was the direction of needed im- 
provement with a view to meeting such unprecedentedly 
exacting requirements. Large losses followed the endeavor to 
introduce the new system of transmission of energy, and enor- 
mous sums were invested only to give disappointment in the 
magnitude of returns, if not by absolute and serious or entire 
loss. About 1890 the true methods of design and of con- 
struction and operation became recognized by many of the 
better class of designers and constructors, and from that 
date steady advance has characterized this field of engineer- 
ing in all its departments. 

One of the most striking gains has been seen in the im- 
provement of the steam-engine for electric-light and -power 
production. It has been given a marvellous accuracy in reg- 
ulation, a fairly high efficiency and moderate cost in con- 
struction and operation. With a single valve the so-called 
" automatic " engine is found economical under average 
conditions, and when of good design up to what were once 
thought high powers — 250 to 350 horse-power. The engine 
with detachable valve-gear, as that of Corliss or of Greene, 
has been hardly less improved, and affords good regulation, as 
well as retains its exceptional standing in its economy of fuel. 
It has even been brought up to speeds of revolution exceed- 
ing 100 per minute, and has been built in forms espe- 



\To /ace page 289.] 




Modern Direct-connected 1,250 H. P. Unit. 



ELECTRIC LIGHTING PLANTS. 2 89 

cially adapted to the peculiar work here demanded of it. 
The latest forms illustrate the compactness of the merchant- 
marine typ«, and these vertical engines are finding place 
wherever land is costly or where, for oth'^r reasons, restricted 
floor-area is desirable. 

The steam-boiler is now usually of the water-tube type^ 
both because of its safety from danger of explosion and its 
peculiar compactness. Numerous automatic accessories, as 
''mechanical stokers," automatic feed-apparatus, and sys- 
tems of carriage of coal and ashes, and even automatic 
weighing-machines, have come into use in large stations. 

The generators in extensive plants have been made of pre. 
viously unimagined sizes and powers ; 1,000, 2,500, and even 
5,000 horse-power dynamo-electric machines being demanded 
and used by engineers proportioning plants for the largest 
distributions and supplied by builders. These machines are 
now nearly all of the multipolar types and generally direct- 
connected. In railway work it is common to connect one 
engine to one dynamo, while in lighting it is quite as usual 
to drive two generators, one from either end of the shaft of 
one engine. 

Alternating machines are now employed in as large pow- 
ers and for even more extensive transmissions, and are 
made for any amount of current up to above 3,000 kilo- 
watt rating, and for any desired method of connection or 
of distribution of current. They are made single-phase or 
multiphase, as needed, and have found their way into use 
with extraordinary rapidity, especially for very long distance 
transmissions. In fact to-day any kind of service may be 
had from any standard form of machine. 



290 



STEAM ENGINES FOR 



Storage-batteries are now in use in many places to reduce 
the irregularity of demand and of supply of electric cur- 




Triple-expansion Engine and Direct-connected Generators. 

rent; thus, by permitting the steady working of the generat- 
ing system, giving opportunity to employ economical pro- 
portions of driving-engines. The tendency of change has 



ELECTRIC LIGHTING PLANTS. 



291 



also led in the direction of, as far as practicable, concen- 
trating the machinery, in order that we may avail ourselves 
of the economical advantage of production in large quantity 




by a single collection of machinery and with a single crew 
of workmen and office employees. The art of distribution 
of stations, where their separation is wise, is well under- 
stood, and maximum economy of povver- and light-produc- 
tion has come to be very generallv nttained. 



292 



STEAM ENGINES FOR 



In recording cost the kilowatt-hour is now usually taken 
as the unit against which it is measured, and this, the 
equivalent of about one and one-third electrical horse- 
power, thus becomes the gauge of the energy received from 
a stated amount of mechanical power expended. On the 
subject of costs Mr. Field remarks : ' 

" The economy of the steam-engine as the generating 
unit driving the electrical generator is one of the main fac- 



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40 fi ( 

PER CENT OF LOAD 



E. H. P. Output per Unit Total H. P. 



tors in the cost in connection with the economy of power- 
station work. The economy of these units, as we stated, 
has been largely improved ; the size of the units has been 
increased, and to-day stations are built with large units, 
adapted for variations of load for which the station is used. 
There is still in many cases, and in fact almost generally, a 
considerable variationi n the economy during the 24 hours, 
with the variations which hold in commercial practice, both 
in railway and lighting work. 

" I do not know that we can better illustrate how this 
variation affects the pounds of coal per kilowatt than to 

I. Cassier's INIagazine, 1896, p. 428. 



ELECTRIC LIGHTING PLANTS. 293 

instance an example which has come under my observation 
in a power-station which is showing one of the best results 
that I know of. The variation in coal consumed per kilo- 
watt during 24 hours is about as follows : From 9 a.m. to 9 
P.M., 45 to 5^ pounds of coal per K. W. hour generated, 
charging everything up to the generation that should be 
charged. For the balance of the 24 hours the results run 
from 54^ to 9f pounds of coal. These figures are startling, 
but they are facts. 

" We further illustrate this by showing the combined 
eflficiency of the generator and engine unit as a whole in the 
figure, showing, at 20 per cent load, an output efficiency 
of about 35 per cent of the ratio between electrical H. P. 
output and total indicated H. P. of the engine ; at about 50 
per cent of the load the efficiency has increased to 80 per 
cent ; at 65 to 70 per cent of the load it is up between 85 
and 87 per cent, and the total efficiency is between 85 and 
90 per cent. The figures show that units should not be 
operated at less than 50 per cent of the capacity, and pref- 
erably at from 65 or 70 per cent. 

" The efficiency-curve of the generator shows that the 
generator holds a higher average efficiency than the engine 
when we compare it with the combined efficiency of the en- 
gine and generator. This shows at 10 per cent of load an 
efficiency of over 70 per cent ; at 25 per cent of load an effi- 
ciency of 82 per cent ; at 50 per cent of load an efficiency 
of ^\\ per cent ; at 75 per cent of load an efficiency of 

93 per cent ; and full load efficiency of between 93 and 

94 per cent. Test records show, in the best power- 
stations, that with an efficiency of, say, three pounds of 



294 



STEAM ENGINES FOR 



coal per K. W.-hour produced, for a unit operating at nor- 
mal load, the station record, charging everything against the 













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coal-consumption for the 24 hours and taking the average 
loads under the best of conditions, would, be about 4^ 
pounds of coal per kilowatt for a week's record. 



ELECTRIC LIGHTING PLANTS, 



295 



"These 3 pounds of coal per K.W.-hour, transferred into 
pounds of water per H. P. generated, would be equivalent 
to about 15 pounds. It should not be understood that 



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P.M. 



Load-diagrams, Central Station. 

the engine will show this continually throughout the 24 
hours, but under normal and constant load only, under the 
best conditions. 

" I have tried to illustrate by some load diagrams an idea 
of the variations of load during different parts of the day for 
central-station lighting and railway work. The figure shows 
two load days in a large central station, the one with the 
more average load being a dark, stormy day in the summer- 
time, and the other being a December day, showing maxi. 
mum load conditions between nine and ten o'clock in the 
morning and between five and six o'clock in the afternoon. 

"The next figure shows an example of a day in another 



296 



STEAM ENGINES FOR 



Station, and on it is given also the average load, which 
shows the following results : Maximum load, 14,000 am- 



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peres ; average load for the day, 5,942 ; total number of 
lights connected to station, both arc and incandescent, 



ELECTRIC LIGHTING PLANTS. 297 



reduced to equivalent in 16 candle-power lamps, 90,000. 
The maximum load of 14,000 amperes is equivalent to, 
approximately, 28,000 sixteen candle-power lights, or about 
31 per cent of those connected. The average load shows 
about 12,000 lights of 16 candle-power or an average of 
about 13 per cent of the connections. This gives a good 
relative idea of the average and maximum loads in a large 
station, and their ratio to the number of lights connected to 
the station, showing that the generating capacity is not 
required to be more than from 30 to 35 per cent of the 
total number of lamps connected, exclusive of reserve. 

" These diagrams also illustrate and show the need and 
requirements of averaging up the load during certain hours, 
by increasing 'the motor load during the light hours and 
offering special inducements to light and other customers 
for increased load during those hours. Electric companies 
have found that they can furnish motor-power for a lower 
price per K. W. than lighting power, because it comes, as a 
rule, during a part of the day when the load is light. 

" To illustrate a railway power curve is a difficult matter. 
The variations of a railway curve are often from maximum 
to minimum within a few moments. In a large station, with 
a large number of cars running, the load takes a more average 
condition and approximates more generally to the curves 
of prominent lighting-stations, showing maximum points 
of load during the morning and evening rush hours when 
people are going to or returning from business. The last 
set of curves illustrates the general average fluctuations of 
load, without indicating the momentary fluctuations. It 



298 



STEAM ENGINES FOR 




3 1 $ Q %' S 9 10 U ^ 
LOAD-DIA RAMS, RAiLWAY-STATION. 



ELECTRIC LIGHTING PLANTS. 



299 



gives also a load diagram showing the average changes for 
the number of cars operated during the entire day. 

" I wish to show by two tables what the cost per kilowatt 
is both for railway and central-station work in the best 




practice to-day and the general results indicated. The cost 
of the manufacture of current per kilowatt-hour in a large 
modern station for lighting, from actual log records, the 



300 STEAM ENGINES FOR 

plant being triple-condensing, with direct-connected gen- 
erators, with steam-pressure of 175 pounds, is as follows : 

Cents. Lbs. 

Water, cost 060 

Coal 4.25 

cost 515 

Removal of ashes. ... -. 026 

Lubrication, waste packing 022 

Labor, engines, boilers, dynamos, and miscellane- 
ous .. 62 

1.243 
Cost of distributing, including care of overhead and 
underground lines, house-wiring, lamp renew- 
als, and meters 767 

2.010 
General executive expenses, including office ex- 
penses, and taxes , 1.55 

Total 3.560 cents, 

or about i.78d. 

" These results show practically i^c. (.625d.) per K. W. 
for manufacture of the current, fc. (-sysd.) for distributing 
the current, and i^c. (.75d.) per K. W. for general and exec- 
utive expenses. This makes the total expenses of the sta- 
tion in question approximately 3|^c. (i.ysd.) per K.W.-hour. 
Going further into this, we find that the coal is approxi- 
mately 40 per cent of the cost of manufacture, labor is 50 
per cent of the cost of manufacture, and the total manu- 
facturing cost is 35 per cent of the whole, with the total 
distributing cost 21 per cent of the whole, and the general 
and executive expenses 44 per cent of the whole. With 
increase of business .the general and executive expenses 
show a smaller percentage of the total ratio. Some stations 



ELECTRIC LIGH7UNG PLANTS. 



show a better average on parts than this one, but I have 
found none that shows a better average as a whole. 

" On railway work, with compound engines and direct- 
connected units, operating at about 130 pounds steam- 
pressure, we have the following results : 

OPERATING EXPENSES. 

Coal at $3.50 (14s.) per ton ^2, 454. 50 (;i^490 i8s.) 

L'abor 1,325.00 {£2t^) 

Oil, waste, and repair 265.50 (^£ 53 8s.) 

Total ^ $4,045.00 (;,^8o9) 

" Taking the total number of cars operated and the car- 
mileage for the month, this being the total expenses for a 
month, we find that the average cost of power per car-mile 
is one cent (|d.), the cars being almost entirely 18-foot 
single-truck cars. The grade conditions and general service 
are the average. Transferring this cost of car-mileage into 
cost per K. W. manufactured, determining this cost both 
from station records and car test of power consumed, we 
have approximately .9c. (.45d.) per K.W.-hour as the cost of 
manufacture, in which the coal is approximately 63 per 
cent of the manufacturing cost, labor 2)Z V^"^ cent, and oil, 
waste, and repairs 4 per cent. 

" I believe we are fast approaching the time when we will 
show, if we are not already doing it, in some stations, a re- 
sult in the cost of manufacture per K.W.-hour equal to one 
cent (|-d.) for lighting-stations and fc. (.375d.) for railway- 
stations. The examples indicated here are authentic cases, 
taken from actual records obtained. 



STEAM ENGINES FOR 



" It may be of further interest to indicate in a general 
way what such a central power station, say one of 5,000 K. W. 
capacity, would cost per K. W. : steam-plant, $85 (:^i7) 
per K. W., including engines, boilers, pumps, heaters, con- 
densers, piping, etc.; electric plant, including generators, 
switchboard, cables, etc., direct-connected units, $30 (p^6) 
per K. W. ; power-station, building under average building 
conditions of good foundations and no rock excavation, 
including foundations, building, stack, etc., $15 (;^3) per 
K. W. ; sundries $10 {£,'2-^ per K. W. This makes a total of 
$140 (^28) per K. W. This is exclusive of real estate." 

In the planning of the steam-engine outfit of large sta- 
tions the relative cost of large and small units must often 
be carefully considered. Thus the illustration shows the 
relative costs of standard engines of an important building 
firm where, for example, two 300 to 500 I. H. P. engines cost 
less than a single machine of double power ; but the value 
of the space to be occupied must also be taken into account 
and the costs of foundation and all running exoenses af- 
fected by choice of size of unit, as well as the relative desir- 
ability of a pair of engines coupled at 90° in the case of 
cross-compounds. 

In the diagram the ordinates measure relative costs, the 
abscissae power developed. The curve would undoubtedly 
differ somewhat with different engines and different shops. 

The direction of change is thus well indicated, as well 
as the present costs of generation of electric energy and its 
distribution. But it would be folly to attempt to predict 
what will be the course of improvement in even the immedi- 
ate future. The whole field is new, and a thousand brilliant 



ELECTRIC LIGHTING PLANTS. 



303 



and well-educated professional men in the department of 
mechanical engineering are working at the thousand of new 
problems continually presenting themselves, in addition to 






300 400 500 

HORSE POWER 

the many old ones, and it may be confidently expected that 
progress will long continue to exhibit itself in peculiarly 
rapid advances in all directions. 

The costs of distribution of powder include, ordi- 
narily, those of overcoming the friction of a large amount 
of shafting and belting. The magnitude of this cost has 
been carefully studied by Mr. Henthorn.' The power 
demanded in cotton and woolen mills is rarely much, if any, 
less than 20 per cent of that furnished by the engine, while 
it sometimes amounts to 30 per cent and over. 

The transmission of steam-power, and the application of 
energy at a distance from the primary source, with 



I. Trans. Am. Soc. M. E , Vol. VI. No. CLXXVII. 



304 STEAM ENGINES FOR 

economy, safety, and certainty, may often prove a problem 
of such importance as to justify a careful study and com- 
parison of all available methods. These methods include : 

(i) Transmission of energy by carriage of steam to 
motors distant from the boilers. 

(2) Transmission of power from engines set beside the 
boilers. 

In the former case the total power may be supplied, 
often, either from a single engine or by supplying the steam 
to a number of smaller engines distributed as may be found 
best in facilitating work ; and the problem includes that of 
determining what arrangement and distribution of these 
engines is, on the whole, most desirable. In the latter case 
the problem includes the comparison of various methods of 
transmission of energy from the engines to the work. 

The transmission of steam is rarely practised over dis- 
tances exceeding a few hundred feet at most, although 
there are no insuperable difficulties, ordinarily, to carrying 
it thousands of feet, the steam-pipes being well clothed, kept 
dry, and thoroughly and automatically drained at all low 
points by traps, separators, or other system. With inter- 
mittent service, however, this method is usually found both 
wasteful and troublesome, especially in meeting the varia- 
tions of length due changing temperatures, and the " water- 
hammer " liable to occur when steam is introduced into cold 
pipes. External drainage of the trenches in which the pipes 
may be laid is quite as important as the internal drainage of 
the pipes themselves. Distances approximating a half-mile 
are thus readily attained. The higher the steam-pressure 
maintained in the pipes in any given case the less the loss of 



ELECTRIC LIGHTING PLANTS. 305 

pressure by friction, and, usually, the less important any 
stated drop of pressure. 

The engines being placed at the boilers, the transmission 
of their power to their work may take place by either of 
several ways : 

(i) By shafting and. pulleys. 

(2) By wire ropes. 

(3) By water-pressure in pipes. 

(4) By compressed air. 
(s) By electric currents. 

For short distances, as within workshops as commonly 
constructed, lines of shafting are safest, cheapest, and in all 
ways best. For driving large isolated and widely dis- 
tributed machines it is often better to adopt a small engine 
for each or at each group, supplied with steam from the 
main boilers, with water or air under pressure from pumps 
driven by the main engine, or with motors driven by 
currents supplied from electrodynaraic generators similarly 
driven. The limit for shafting, as an average, may be 
taken as about 1,000 feet ; but the coefficient of friction of 
shafting, under its light pressures, is very great ; the fric- 
tion is intensified and power wasted by the often inevitable 
"getting out of line," and the weight is considerable, so 
that the total waste is apt to be serious. In such cases the 
engine distributing its power should be as near the center 
of power utilization as possible. 

All pulleys should be carefully balanced and should "run 
true." All others should be promptly condemned. Tubu- 
lar shafting has the advantage of stiffness, the disadvantage 
of large friction. Belting is used under all ordinary condi- 



3o6 STEAM ENGINES FOR 

tions ; but it is unfitted either for the transmission of exact 
velocity-ratios or for slow speeds of rotation and large 
power. 

AVhere the span is considerable and no shafting is de- 
sired, ropes of hemp, cotton, or wire are often employed in' 
place of belts, and 50 H. P. per rope, if hemp or cotton, of 
7 inches circumference, at 1,500 feet per minute, is consid- 
ered good practice. AVith such ropes arranged " in multi- 
ple " great care must be exercised to see that their pulleys 
are precisely alike in size. Chains may be used instead of 
belting for very slow and heavy work. 

Wire-rope transmission is employed very extensively for 
long distances, the carrying-pulleys being set at distances of 
200 to 500 feet apart, and made of a diameter usually not 
less than 100 times that of the rope, and preferably 150. It 
is found that distances of 10 miles or more may be thus 
attained with a loss not exceeding 25 per cent. 

Water-presstire of great intensity, with flow at a moderate 
rate, often proves a satisfactory system of distribution for 
moderate distances. An " accumulator " receives the water 
from the pumps and equalizes the pressure and flow. The 
incompressibility and fluidity of the liquid especially fit it 
for such use where the line of transmission is tortuous and 
irregular. Water taken from the street-mains is often used, 
under pressures of from 30 to sometimes 100 pounds per 
square inch. The higher the safe pressure the better, 
however ; and a special supply at pressures exceeding 300 
or even 700 and 1,000 pounds is frequently found best. 
This system is often adopted for riveting-machines and 
other portable hydraulic tools and macliines. Water-pres- 



ELECTRIC LIGHTING PLANTS. 307 

sure is especially limited to cases in which the power is 
needed irregularly or at long intervals, when the work con- 
sists in the operation of reciprocating motors or machines, 
when irregular accumulation, as by windmills, is practi- 
cable, and where exceptionably great pressures are de- 
manded. 

Compressed air is used in cases somewhat similar to the 
preceding, and has been found especially suitable for min- 
ing operations, where water would be liable to freeze, and 
more particularly when hieh-speed rotation motors, and 
machines like rock-drills, are to be driven. It is, however, 
very wasteful of power, and in large operations it has often 
been found that no more than 25 per cent efficiency 
in transmission could be attained, high pressures being em- 
ployed. This loss is in compression, largely ; the loss by 
friction in pipes is not so large, and should not exceed 5 
per cent per mile. For driving small motors, however, the 
advantages of air are often great, and it is sometimes ex- 
tensively used for this purpose. Its value in underground 
work is often greatest as supplying ventilation in otherwise 
inaccessible places. Moderate pressures, rarely exceeding 
100 pounds, are used. Any form of motor that can be 
driven by steam may be used with air. For other than 
power purposes low pressures should be employed. 

Electric transmission is finding extensive use in power- 
distribution, as is perhaps best illustrated by the systems 
of electric street-railway, and of supplying power for the 
minor industries. As in lighting, either the continuous 
current or the alternating may be used, although the former 
is the more generally adopted ; and the continuous current 



3o8 STEAM ENGINES FOR 

•— 

may be furnished either by a generator direct or by a 
storage-battery. 

A net efficiency of generator and motor together not less 
than 75 per cent should be attained. The loss on the line 
is very uncertain and variable. A tension of about 500 or 
600 volts is usual. 

The choice of this system is determined by a comparison 
of total costs. The losses enormously increase as the size 
of conductor in proportion to power transmitted diminishes. 
High tensions give great economy in this respect, while in- 
creasing leakage. Costs of conductors constitute a heavy 
tax on the system for long-distance transmission, and 2 to 
5 miles may be taken as the ordinary range of practically 
attainable maxima. 

This method has peculiar advantages for street-railway 
work, and has come into use mainly in that direction. 
Where lighting-" plants " are already installed, it is often 
found that the addition of a power system is economical 
and convenient, as well as otherwise desirable. 

The cost of generating poAver from a fall of 80 feet as re- 
ported by Mr. Holt as obtained by dividing the cost of 
labor and lubricants (interest and depreciation are not in- 
cluded) by the horse-power demanded amounts at present 
to less than two-thirds of one cent per horse-power per 
hour, up to IOC horse-power.' 

The advantages of electrical power for mining operations 
are : "^ 

(i) It can be transmitted over long distances with small 



1. Trans. Am. Inst. Min. Engrs, Oct.., 1891. 

2. Ibid. 



ELECTRIC LIGHTING PLANTS. 3^9 

loss, making it possible to use power at such a distance from 
its source as would render it otherwise unavailable. 

(2) The conductors for conveying electrical power require 
no appreciable space, are easily put in place and repaired, 
are easily tapped for branch circuits, and form a flexible 
system throughout. 

(3) The electrical system is ideal in its cleanliness. 

(4) The stations can be made to occupy a minimum of 
space. 

A good illustration of the flexibility of the system is the 
diamond drill ; in its use the conductors are unwound and 
strung up as the drill moves along, or taken down and coiled 
up, as may be found convenient. 

The waste of power from friction-resistance in the case 
of transmission by shafting is usually roughly stated at one 
per cent per one hundred feet, giving an ultimate limit at 
about ten thousand feet, or less than two miles, beyond 
which it is absolutely useless, and making it usually practi- 
cally undesirable in lengths exceeding a few hundred feet. 
With electrical distribution this increase of waste with 
lengthening traverse is much less, and Beringer makes the 
total cost vary as the third or fourth root of the distance, 
increasing the more slowly as the power is the greater. 
Wire-rope transmission has a limit at three or four times 
that of shafting, or, commonly, five or six miles. Below a 
maximum of two to three miles this is, at present, the 
cheapest transmission ; for higher figures the electrical is 
best. Practically the latter would, in most cases, be used 
beyond a mile. 

Beringer has compared the four principal systems of power- 



3IO STEAM ENGINES FOR 

transmission, by water, air, rope, and electricity, and finds 
the latter usually best.' Wire rope is found most economi- 
cal for short distances, as between loo feet and a half or 
three-quarters of a mile, under the conditions assumed ; but 
electricity is preferable beyond that maximum. Hydraulic 
and pneumatic systems cost much more, although the latter 
approximates the best figures at high powers and long dis- 
tances, and all. are more nearly alike as power transmitted 
and distances increase. Where air is wanted for ventilation, 
as in some mining operations, it often displaces all other 
methods. Electricity is now finding many applications in 
mining as well as in other power-transmissions. 

It seems probable that these comparisons made with old 
and familiar systems may be altered somewhat, if not to an 
important extent, in favor of compressed-air transmission 
by adopting improved apparatus and methods — for example, 
as illustrated by the Popp distribution in Paris. By more 
effective spray-cooling at the point of compression, and by 
the adoption of a good compound type of compressor. Pro- 
fessor Riedler found it practicable to reduce the wastes 
from 43 to 12 per cent. By reheating the air at entrance 
into the engines at the other end of the system Popp ob- 
tains, according to Professors Gutermuth and Weyrauch, a 
transformation of 70 per cent of the heat thus added into 
useful work, and a net gain of final efficiency of 30 per cent 
by raising the temperature of the working charge to 250° C. 
{482° F.). By compounding the motors and reheating 
between the two in series Riedler reduced the consump- 
tion of air from 812 cubic feet per hour per brake horse- 

I. Kritische Vergleichung der Electrischen Kraft-ubertragung, 1883. 



ELECTRIC LIGHTING PLANTS. 311 

power to 646 with the steam-engine form and with rotary 
motors from 1,059 ^^ ^47 '■> the machines being in both cases 
of rude construction, inefficient type, and very small size. 
The investigators of this system consider it possible that it 
may prove, on the whole, the most economical method of 
power-transmission. ' 

The losses are always considerable. Thus at St. Far- 
geau, Paris, air is compressed by the Popp Company to 6 
atmospheres, sent 5 kilometers, and operates compressed- 
air engines at a pressure of \\ atmospheres and an efficiency 
of 0.26. Compound compressors, however, may sometimes 
save a large proportion of the Avaste heat of compression, 
raising the efficiency of the compressor from 50 or 60, or from 
at most 70, to 85 or 90 per cent.^ Good compressors and 
good engines should give at least 0.85 for the efficiency of the 
machine ; and compressors should return from 70 to 90 per 
cent of the work expended upon them. Professor Unwin 
has computed a transmission for 10,000 H. P. twenty miles 
through mains 30 to 50 inches diameter, at an initial pres- 
sure of 75 to 190 pounds, and velocities of flow of 20 to 50 
feet per second, with resultant efficiencies varying from 40 
to 50 per cent, or if the air be heated at the engine of 60 
to 73 per cent. ^ 

The costs and profits per mile run of street-railway power- 
transmission in Birmingham, G. B., all under a common 
management, were reported in 1891 as below : * 

1. London Engineering, iSgi ; Scientific American Supplement, May 23, 1891. 

2. Riedler : Neue Erfahrungen iiber die Kraft-versorgung von Paris durch Druck- 
luft, Berlin, 1891. 

3. Trans. Brit. Inst. C. E., 1891, No. 2548, Vol. CV. Part III. See also Vol. XCIII. 

p. 421- 

4. Engineering, Aug., 1891 ; Iron Age, Sept. 3, 1891. 



312 STEAM ENGINES FOR 

Costs. Earnings. Profits. 

Steam-plant 21.98 3i-34 9-36 

Wire cable 12.66 24.06 11.40 

Electric 19.80 30.30 10.50 

Horse i9-S8 22.04 2.46 

Running expenses only are included. Interest and repairs 
should be added. The order given is that of amount of 
traffic, the steam '' cars " doing most work. 

It will be usually found that each system is well adapted 
to a special set of economical conditions, and that neither 
can satisfactorily replace the other. 

Relay poiver is demanded at times as accessory to the 
regular and usual motive power, either where streams 
supply water-power in varying quantity throughout the 
year, or where the load is itself varying and irregularly ap- 
plied from day to day or season to season. In such instances 
steam-power is resorted to at times to supplement the tem- 
porary deficiency ; and the kind, size, and economical value 
of the "relay" motor must be carefully considered. 

In general, it may be said that if required for a longer time 
it must usually be more economical than if worked only a 
short time or for a small portion of the year, as is evident 
from the considerations studied in connection with problems 
of commercial efficiency. If used but seldom or for but a 
brief period, low first cost is the primary consideration ; if 
for long periods, economy of operation must determine the 
size and character of the engine and its boilers. 

Whatever the proportion of time in use, however, the 
engine should as far as possible conform to the primary re- 
quirement : 



ELECTRIC LIGHTING PLANTS. 3^3 

Minimum total cost of annual operation, including all the 
items enumerated when considering the problem of maxi- 
mum commercial efficiency. 

To this the following are accessory or subsidiary. 

(i) Minimum first cost, consistent with the dernanded 
efficiency. 

(2) Efficiency adjusted to meet the primary demand 
above. 

(3) Permanence of efficiency, despite the specially adverse 
•circumstances of its use. 

(4) Permanent good condition, though out of use. 

(5) Stability of foundations and machinery of transmis- 
sion. 

(6) Minimum trouble and expense in "laying up" and 
-again starting. 

(7) Independence of skilled attendance. 

The cost of machinery of transmission, whether by belting 
or gearing, and especially the loss of the power absorbed by 
its friction, often makes it advisable to avoid its use as far as 
practicable, and to use separate engines for widely separated 
machines. This is especially the case in mills and other 
establishments in which the transmitting machinery consti- 
tutes a heavy and continuous load, while the driven 
machinery is operated only at intervals, and even, as is often 
the case, at long intervals and for brief periods of time. A 
judicious distribution of motors in such instances will often 
effect an enormous annual saving. It must, however, always 
be considered that, other things equal, several small engines 
will demand more steam than a single engine of equal total 
power. 



314 STEAM ENGINES FOR 

The irregular demand at electric-lighting stations illus- 
trates a peculiar case of what in a sense may also be termed 
" relay power," and the matter of subdivision of motive 
power and the problem arising out of it must often be set- 
tled by a study of existing "plants" and by reference to^ 
earlier experience. The experiments of Dr. Louis Bell 
being compared with those directly reported to the author 
indicated a total efficiency of but 25 per cent with large 
engines and of 37 per cent with small engines directly 
connected, the work being that of street-railways ; but 
enormous variations are produced by differences in design, 
construction, and method of operation.' 

Safety devices employed on engines having detachable 
valve-gearing, when effective, insure against the often dis- 
astrous consequences of a "runaway" when the load sud- 
denly drops or is, as sometimes occurs, all thrown off. In 
this class of engines such sudden removal of load, and the 
consequent jump of the engine under the steam-supply at 
the moment before introduced to carry the heavier or the 
full load, is liable to cause dangerous increase of speed, or 
even, by slipping the governor-belt or throwing it off, to 
produce very rapid acceleration up to the speed at which 
the wheel can no longer withstand the centrifugal forces 
acting upon it. The consequence has often been the rup- 
ture of the fly-wheel and the complete destruction of the 
engine, with even more serious consequences in loss of life 
and property by the scattering of parts of the engine with 
the impetus of a cannon-shot. No engine of this class 
should be employed where great fluctuations of speed are 

I. Electrical World, Aug.j6, 1890,. p. 103. 



ELECTRIC LIGHTING PLANTS. 315 

likely to take place, and they are not entirely free from such 
danger even where, as in cotton-mills, the load is com- 
monly very steady. Accidents of this kind have often 
happened in electric-light and power stations, especially in 
the power-stations of electric railways. They have taken 
place in a number of instances in mills. 

The " automatic " engine with its shaft-governor of the 
Hartnell class is not liable to this particular kind of acci- 
dent, since any accident to its governor system stops the 
engine immediately by interrupting the supply of steam. 

Costs. — The following were fair average figures for costs 
of construction in 1895, but are subject to continual varia- 
tion with the state of the market : ' 

COST OF STEAM AND ELECTRICAL PLANTS— COST OF 
ENGINES FOR SIZES OVER 100 H. P. 

High-speed, single $11 to $13 per H. P. 

" compound 14 " 16 " " 

Corliss, single 16" 18 " " , 

" compound 22 " 25 " " 

triple 27 " 30 " " 

COST OF STEAM-PLANTS, 

INCLUDING ENGINES, BOILERS, PIPING, PUMPS, HEATERS, FOUNDA- 
TIONS, SETTINGS, ETC. 

High-speed $40 to $50 per H. P. 

Corliss, direct connection 60 " 7° " *' 

counter-shaft 80 " 85 " " 

COST OF ELECTRICAL PLANT. 
Dynamos, switchboard, cables, foun- 
dations, erecting, etc $35 to $40 per H. P. 

1. Manual of the Steam Engine. R. H. Thurston (N. Y., J. Wiley & Sons), Vol. II- 
pp. 887 et seq. 



li il 



<f (( 



316 STEAM ENGINES FOR 

Pole-line, including mains, feeders, 

poles, setting, etc 4 " 6 " 16 C. P. 

Underground ditto 7 " 9 

Inside wiring, including lamp, socket, 
plain pendant and rubber-cov- 
ered wire, moulded work 4 " 5 

Same, for concealed work 5 " 6 " " " 

Mr. Field gives the following figures for a case of the 
purchase, equipment, and operation of a street-railway sys- 
tem with electricity, a city witn a population of say 100,000 
— with a dilapidated street-railway system, earning a gross 
income of $125,000, to purchase same for $500,000 — prop- 
erty rights, franchises, etc., and equip it with 40 miles of 
single track and 65 electric cars : ' 



COST OF EQUIPMENT. 

Steam-plant (1,500 H. P. steam-plant) : 
Five engines, 250 H. P. each, compound 
condensing, size 16 in. X 32 in. X 42 

in., with wheels weighing 30,000 lbs.. $32,500 

Eight R. T. boilers, 72 in. X 16 ft 9,600 

Jet-condensers • - 3,000 

Two boiler-feed pumps 900 

Steam- and exhaust-piping 12,000 

Five engine-foundations 3, 500 

Eight boiler-settings 3,200 

Five 30-in. belts 2,000 

Erecting and starting 3»5oo 

Freight and miscellaneous 2,500 

$72,700 

I. Trans. Nat. El. Lt. Assoc, Montreal Meeting, 1891. 



ELECTRIC LIGHTING PLANTS. 317 

Electrical plant : 

Five generators, 200 kilowatts $37)5°° 

Switchboard installation, foundations, etc. 4,000 

41,500 



Building : 
Power-station, including stack, traveling 

crane, etc » $25,000 

Car-house and repair-shop, including 

tools, etc 15,000 



Track-construction : 
Forty miles girder-rail construction, ties 

2\ ft. centers, 63-lb. rail, etc., $1.15 

per foot $242,880 

Relaying, including paving, etc., at 60 

cents per foot 126,720 

Trucking, hauling, etc. , , 24,000 

Ties, including 10 per cent of joint ties, 

130,000 at 40 cents , 52,000 

Ties, including 10 per cent of joint ties, 

15,000 at 70 cents 10,500 



40,000 



456,100 

Line-construction : 

Ten miles iron poles, etc $75,000 

Ten miles wooden poles, etc 40,000 

115,000 

Car-equipment : 

65 electrical equipments at $2,000 $130,000 

65 car-bodies, 18-foot body, with open ends. 65,000 

65 trucks at $250 16,250 

211,250 



3i8 STEAM ENGINES EOR 

Summary : 

Steam-plant $72,700 

Electrical plant 41,500 

Building 40,000 

Track. 456,100 

Line-construction 115,000 

Car-equipment 211,250 

$936,550 

Superintendent's and engineer's 

work $50,000 

General and miscellaneous 50,000 

100,000 

$i,o35>55o 
Original purchase 500,000 

Total cost re-equipped $i>535)55o 

Gross income, say, $350,000. 

The transmission or power over very great distances, as 
from a waterfall or prime motor to a town or an establish- 
ment several miles away, is best effected by the electric cur- 
rent at high tension, as to London from Greenwich by the 
Ferranti system, or from the Neckar Falls at Dauffen to 
Frankfort, Germany. The latter is about no miles (180 kil- 
ometers), and a " pressure " of 25,000 volts is adopted by its 
designers, the Oerlikon Works, and 300 electrical horse- 
power is transmitted. 

In the organization of such a system of distribution the 
division of duties is somewhat as follows : ' 

The superintendent is in charge of the station and of all 
work. If the station is large enough, he may have a man 
who can attend to the making out of reports. His assistant 

I, Trans. Nat. El. Lt. Assoc, 1890. 



ELECTRIC LIGHTING PLANTS. 319 

takes his place at times, and can often decide whether work 
shall be done, or whether it shall wait for the superintend- 
ent's return. 

Under the superintendents are the chief engineer, chief 
dynamo-man, chief lineman, and chief incandescent wire- 
man. 

Under the chief dynamo-man are various dynamo-runners, 
although the chief engineer may be able to take charge of 
the dynamo-room. 

Under the chief engineer are all engineers, foremen, coal- 
handlers, etc. 

In the absence of the chief engineer, the engineer on 
watch takes his place, and the same with regard to the 
dynamo-man. 

The chief lineman should have under his care pole-lines, 
outside construction of all kinds, including all arc-lamps and 
high-tension wires ; also the care of converters, if any, to the 
first cut-out on the secondary side. He should also have 
charge of the carbon-setters and arc patrolmen. 

The chief wireman should have charge of inside wires, all 
lamp-renewals, patrolmen, and material and work. 

The storekeeper has duties separate from all these. 

The reports necessary are the engineer's log, for which 
there should.be two books provided, — one for the day run, 
and one for the night run, — to be filled up by the engineer 
on watch and turned into the superintendent's ofifice each 
day for examination. 

The dynamo-room log should include a reading of the load 
on each machine, taken at twenty-minute intervals through- 
out the whole run. This report, with the amount of coal 



320 STEAM ENGINES FOR ELECTRIC PLANTS. 

burnt, gives a check on the fireman and the quality of 
coal. 

The inspectors and patrolmen should fill out a form, giv= 
ing the number of arc-lamps on the circuits ; if any are out 
or burning badly, between what hours, and the probable 
cause. 

The storekeeper should make a report daily of all material 
received and issued, which can be used as a check upon bills 
/or material. 




SHORT-TITLE CATALOGUE 

OF THE 

PUBLICATIONS 

OF 

JOHN WILEY & SONS, 

New York. 
London: CHAPMAN & HALL, Limited. 



ARRANGED UNDER SUBJECTS. 



Descriptive circulars sent on application. 

Books marked with an asterisk are sold at net prices only. 

All books are bound in cloth unless otherwise stated. 



AGRICULTURE. 

Cattle Feeding— Daiey Practice — Diseases of Animals — 
Gardening, Etc. 

Armsby's Manual of Cattle Feeding 12mo, $1 75 

Downing's Fruit and Fruit Trees 8vo, 5 00 

Grotenfelt's The Principles of Modern Dairy Practice. (Woll.) 

12mo, 2 00 

Kemp's Landscape Gardening 12mo, 2 50 

Loudon's Gardening for Ladies. (Downing.) 12mo, 1 50 

Maynard's Landscape Gardening 12mo, 1 50 

Steel's Treatise on the Diseases of the Dog 8vo, 3 50 

" Treatise on the Diseases of the Ox 8vo, 6 00 

Stockbridge's Rocks and Soils Svo, 2 50 

WoU's Handbook for Farmers and Dairymen 12mo, 1 50 

ARCHITECTURE. 

Building — Carpentry — Stairs — Ventilation — Law, Etc. 

Berg's Buildings and Structures of American Railroads 4to, 7 50 

Birkmire's American Theatres — Planning and Construction. Svo, 3 00 

" Architectural Iron and Steel Svo, 3 50 

" Compound Riveted Girders Svo, 2 00 

" Skeleton Construction in Buildings Svo, 8 00 

1 



Birkmiie's Planning and Const ruction of High Office Buildings. 

8vo, 13 50 

Carpenter's Heating and Ventilating of Buildings 8vo, 3 00 

Freitag's Architectural Engineering 8vo, 2 50 

Gerhard's Sanitary House Inspection 16mo, 1 00 

" Theatre Fires and Panics 12mo, 1 50 

Hatfield's American House Carpenter 8vo, 5 00 

Holly's Carpenter and Joiner 18uio, 75 

Kidder's Architect and Builder's Pocket-book. . .ICmo, morocco, 4 00 

Merrill's Stones for Building and Decoration 8vo, 5 00 

Monckton's Stair Building — "Wood, Iron, and Stone 4to, 4 00 

Wait's Engineering and Architectural Jurisprudence 8vo, 6 00 

Sheep, 6 50 
Worcester's Small Hospitals — Establishment and IMaiutenauce, 
including Atkinson's Suggestions for Hospital Archi- 
tecture 12mo, 1 25 

World's Columbian Exposition of 1893. Large 4to, 2 50 

ARMY, NAVY, Etc. 

Military Engineeking— Ordnance — Law, Etc. 

Bourne's Screw Propellers 4to, 

Bruff's Ordnance and Gunnery 8vo, 

Chase's Screw Propellers 8vo, 

Cooke's Naval Ordnance 8vo, 

Cronkhite's Gunnery for Non-com. Officers 32mo, morocco, 

Davis's Treatise on Military Law 8vo, 

Sheep, 

" Elements of Law 8vo, 

De Brack's Cavalry Outpost Duties. (Carr.). . . .32mo, morocco, 

Dietz's Soldier's First Aid 16mo, morocco, 

* Dredge's Modern French Artillery Lagre 4to, half morocco, 

" Record of the Transportation Exhibits Building, 
World's Columbian Exposition of 1893.. 4to, half morocco, 

Durand's Resistance and Propulsion of Ships 8vo, 

Dyer's Light Artillery 12mo, 

Hoflf's Naval Tactics 8vo, 

Ingalls's Ballistic Tables 8vo, 

" Handbook of Problems in Direct Fire 8vo, 

2 



5 00 


6 00 


3 00 


12 50 


2 00 


7 00 


7 50 


2 50 


2 00 


1 25 


15 00 


10 00 


5 00 


3 00 


1 50 


1 50 


4 00 



$1 50 


7 50 


2 00 


4 00 


5 00 


1 50 


10 


2 50 


4 00 


1 50 


3 50 


2 00 


2 50 


1 50 


2 00 


1 00 



Miiliau's Advanced Guard 18ino, 

" Permanent Fortifications. (Mercur.).8vo, half morocco, 
Mercur's Attacli of Fortified Places 12mo, 

" Elements of the Art of War 8vo, 

Metcalfe's Ordnance and Giuinery 12mo, with Atlas, 

Murray's A Manual for Courts-Martial IGino, morocco, 

" Infantry Drill Regulations adapted to the Springfield 

Rifle, Caliber ,45 33mo, paper, 

Phelps's Practical Marine Surveying Bvo, 

Powell's Army Officer's Examiner ISmo, 

Sharpe's Subsisting Armies 32mo, morocco, 

Very's Navies of the World 8vo, half morocco, 

Wheeler's Siege Operations 8vo, 

Wiuthrop's Abridgment of Military Law 12mo, 

Woodhull's Notes on Military Hygiene IGmo, 

Young's Simple Elements of Navigation.. IGmo, morocco flaps, 

" " " " " first edition 

ASSAYING. 

Smelting — Ore Dressing— Alloys, Etc. 

Fletcher's Quant. Assaying with the Blowpipe.. 16mo, morocco, 1 50 

Furman's Practical Assaying 8vo, 3 00 

Kunhardt's Ore Dressing 8vo, 1 50 

O'Driscoll's Treatment of Gold Ores 8vo, 2 00 

Ricketts and Miller's Notes on Assaying 8vo, 3 00 

Thurston's Alloys, Brasses, and Bronzes 8vo, 2 50 

Wilson's Cyanide Processes 12mo, 1 50 

" The Chlorination Process 12mo, 150 

ASTRONOMY. 

Practical, Theoretical, and Descriptive. 

Craig's Azimuth 4to, 3 50 

Doolittle's Practical Astronomy 8vo, 4 00 

Gore's Elements of Geodesy 8vo, 2 50 

Hayford's Text-book of Geodetic Astronomy 8vo. 3 00 

Michie and Harlow's Practical Astronomy 8vo, 3 00 

White's Theoretical and Descriptive Astronomy 12mo, 2 00 

8 



BOTANY. 

Gakdening for Ladies, Etc. 

Baldwin's Orchids of New England Small 8vo, $1 50 

Loudon's Gardening for Ladies. (Downing.) 12mo, 1 50 

Thome's Structural Botany 16mo, 2 25 

Westermaier's General Botany. (Schneider.) 8vo, 2 00 

BRIDGES, ROOFS, EtCo 

Cantilever — Draw — Highway — Suspension. 

{See also Engineering, p. 7. ) 

Boiler's Highway Bridges 8vo, 2 00 

* " The Thames River Bridge 4to, paper, 5 00 

Burr's Stresses in Bridges Svo, 3 50 

Crehore's Mechanics of the Girder Svo, 5 00 

Dredge's Thames Bridges 7 parts, per part, 1 25 

Du Bois's Stresses in Framed Structures Small 4to, 10 00 

Foster's Wooden Trestle Bridges 4to, 5 00 

Greene's Arches in Wood, etc Svo, 2 50 

" Bridge Trusses Svo, 2 50 

Roof Trusses Svo, 125 

Howe's Treatise on Arches Svo, 4 00 

Johnson's Modern Framed Structures Small 4to, 10 00 

Merrimau & Jacoby's Text-book of Roofs and Bridges. 

Part L, Stresses Svo, 2 50 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Part II.. Graphic Statics Svo, 2 50 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Part III., Bridge Design Syo, 2 50 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Part IV., Continuous, Draw, Cantilever, Suspension, and 

Arched Bridges Svo, 

* Morison's The Memphis Bridge Oblong 4to, 

Waddell's Iron Highway Bridges Svo, 

" De Pontibus (a Pocket-book for Bridge Engineers). 

16mo, morocco, 

Wood's Construction of Bridges and Roofs .Svo, 

Wright's Designing of Draw Spans. Parts I. and II.. Svo, each 

" " " " " Complete Svo, 



2 50 


10 00 


4 00 


3 00 


2 00 


2 50 


3 50 



CHEMISTRY. 

Qualitative — Quantitative— Organic — Inorganic, Etc. 

Adriaiice's Laboratory Calculations 12mo, |1 25 

Allen's Tables for Iron Analysis 8vo, 3 00 

Austen's Notes for Chemical Students 12mo, 1 50 

Bolton's Student's Guide in Quantitative Analysis 8vo, 1 50 

Classen's Analysis by Electrolysis. (HerrickandBoltwood.).8vo, 3 00 

Crafts's Qualitative Analysis. (Scbaeffer.) 12mo, 1 50 

Drecbsel's Chemical Eeactions. (Merrill.) 12mo, 1 25 

Fresenius's Quantitative Chemical Analysis. (Allen.) 8vo, 6 00 

" Qualitative " " (Johnson.) 8vo, 3 00 

(Wells.) Trans. 

16th German Edition 8vo, 5 00 

Fuertes's Water and Public Health 12mo, 1 50 

Gill's Gas and Fuel Analysis 12mo, 1 25 

Hammarsten's Physiological Chemistry. (Mandel.) 8vo, 4 00 

Helm's Principles of Mathematical Chemistry. (Morgan). 12mo, 1 50 

Kolbe's Inorganic Chemistry 12mo, 1 50 

Ladd's Quantitative Chemical Analysis 12mo, 1 00 

Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 00 

Lob's Electrolysis and Electrosynthesis of Organic Compounds. 

(Lorenz.) 12mo, 1 00 

Mandel's Bio-chemical Laboratory 12mo, 1 50 

Mason's Water-supply 8vo, 5 00 

" Examination of Water. {In tJie press.) 

Miller's Chemical Physics * Bvo, 2 00 

Mixter's Elementary Text-book of Chemistry ,12mo, 1 50 

Morgan's The Theory of Solutions and its Results 12mo, 1 00 

Nichols's Water-supply (Chemical and Sanitary) 8vo, 2 50 

O'Brine's Laboratory Guide to Chemical Analysis 8vo, 2 00 

Perkins's Qualitative Analysis 12mo, 1 00 

Pinner's Organic Chemistry. (Austen.) 12mo, 1 50 

Poole's Calorific Power of Fuels. 8vo, 3 00 

Ricketts and Russell's Notes on Inorganic Chemistry (Non- 
metallic) , Oblong 8vo, morocco, 75 

Ruddiman's Incompatibilities in Prescriptions Bvo, 2 00 

Schimpf's Volumetric Analysis 12mo, 2 50 

Spencer's Sugar Manufacturer's Handbook . 16mo, morocco flaps, 2 00 



Spencer's Handbook for Chemists of Beet Sugar Houses, 

16mo, morocco, $3 00 

Stockbridge's Eocks aud Soils 8vo, 2 50 

Van Deventer's Physical Chemistry for Beginners. (Boltwood.) 

12mo, 

Wells's luorgaiiic Qualitative Analysis 12mo, 1 50 

" Laboratory Guide in Qualitative Chemical Analysis. 

8vo, 1 50 

Whipple's Microscopy of Drinkiug-water 8vo, 

Wiechmanu's Chemical Lecture Notes 12mo, 3 00 

" Sugar Analysis Small 8vo, 2 50 

Wulling's Inorganic Phar. and Med. Chemistry 12mo, 2 00 

DRAWING. 

Elementary — Geometrical — Mechanical — Topographical. 

Hill's Shades and Shadows aud Perspective 8vo, 2 00 

MacCord's Descriptive Geometry 8vo, 3 00 

" Kinematics 8vo, 5 00 

" Mechanical Drawing 8vo, 4 00 

Mahan's Industrial Drawing. (Thompson.) 2 vols., 8vo, 3 50 

Reed's Topographical Drawing. (H. A.) 4to, 5 OO 

Reid's A Course in Mechanical Drawing 8vo. 2 00 

" Mechanical Drawing and Elementary Machine Design, 
8vo. {In the press.) 

Smith's Topographical Drawing. (Macmillan.) 8vo, 2 50 

Warren's Descriptive Geometry 2 vols., 8vo, 3 50 

" Drafting Instruments 12mo, 1 25 

' ' Free-hand Drawing 12mo, 1 00 

" Linear Perspective ,..12mo, 100 

" Machine Construction 2 vols., 8vo, 7 50 

" Plane Problems 12mo, 125 

" Primary Geometry 12mo, 75 

" Problems and Theorems 8vo, 2 50 

" Projection Drawing , 12mo, 150 

Shades and Shadows 8vo, 3 00 

" Stereotomy— Stone-cutting.. 8vo, 2 50 

Wlielpley's Letter Engraving 12mo, 2 00 



ELECTRICITY AND MAGNETISM. 

Illumination — Batteries — Physics. 

Antbony and Brackett's Text-book of Physics. (Magie.). .8vo, $3 00 

Authoiiy's Theory of Electrical Measurements 12mo, 1 00 

Barker's Deep-sea Soundings 8vo, 2 00 

Benjamin's Voltaic Cell 8vo, 3 00 

History of Electricity 8vo 3 00 

Cosmic Law of Thermal Repulsion 12mo, 75 

Crehore and Squier's Experiments with a New Polarizing Photo- 
Chronograph 8vo, 8 00 

* Dredge's Electric Illuminations. . . .2 vols., 4to, half morocco, 25 00 

Vol. II 4to, 7 50 

Gilbert's De magnete. (Mottelay.) 8vo, 2 50 

Holman's Precision of Measurements 8vo, 2 00 

" Telescope-mirror-scale Method Large 8vo, 75 

Michie's Wave Motion Relating to Sound and Light 8vo, 4 00 

Morgan's The Theory of Solutions and its Results 12mo, 1 00 

Niaudet's Electric Batteries. (Fishback.) 12mo, 2 50 

Pratt and Alden's Street-railway Road-beds 8vo, 2 00 

Reagan's Steam and Electric Locomotives 12mo, 2 00 

Thurston's Stationary Steam Engines for Electric Lighting Pur- 
poses 12mo, 

Tillman's Heat 8vo, 1 50 

ENGINEERING. 

Civil — Mechanical — Sanitary, Etc. 

{See also Bridges, p. 4 ; Hydraulics, p. 9 ; Materials op En- 
GiNEERixG, p. 10; Mechanics and Machinery, p. 12 ; Steam 
Engines and Boilers, p. 14.) 

Baker's Masonry Construction 8vo, 5 00 

" Survejdug Instruments 12mo, 3 00 

Black's U. S. Public Works Oblong 4to, 5 00 

Brooks's Street-railway Location 16mo, morocco, 1 50 

Byrne's Highway Construction 8vo, 5 00 

" Inspection of Materials and Workmanship 16mo, 3 00 

Carpenter's Experimental Engineering Bvo, 6 00 

7 



Church's Mechanics of EngineeriDg — Solids and Fluids 8vo, $6 00 

" Notes and Examples in Mechanics 8vo, 2 00 

Crandall's Earthwork Tables 8vo, 1 50 

' ' The Transition Curve 16mo, morocco, 1 50 

*Dredge's Penn. Railroad Construction, etc. . . Folio, half mor., 20 00 

* Drinker's Tunnelling 4to, half morocco, 25 00 

Eissler's Explosives — Nitroglycerine and Dynamite Svo, 4 00 

Folwell's Sewerage Svo, 3 00 

Fowler's Coffer-dam Process for Piers Svo. 2 50 

Gerhard's Sanitary House Inspection 12mo, 1 00 

Godwin's Railroad Engineer's Field-book 16mo, morocco, 2 50 

Gore's Elements of Geodesy Svo, 2 50 

Howard's Transition Curve Field-book.. . . .12mo, morocco flap, 1 50 

Howe's Retaining Walls (New Edition.) .....12mo, 1 25 

Hudson's Excavation Tables. Vol. II , Svo, 1 00 

Hutton's Mechanical Engineering of Power Plants Svo, 5 00 

Johnson's Materials of Construction Large Svo, 6 00 

" Stadia Reduction Diagram. .Sheet, 22^ X 2Si inches, 50 

" Theory and Practice of Surveying Small Svo, 4 00 

Kent's Mechanical Engineer's Pocket-book 16mo, morocco, 5 00 

Kiersted's Sewage Disposal 12mo, 125 

Mahan's Civil Engineering. (Wood.) Svo, 5 00 

Merriman and Brook's Handbook for Surveyors. . . .16mo, mor., 2 00 

Merriman's Geodetic Surveying Svo, 2 00 

" Retaining Walls and Masonry Dams Svo, 2 00 

" Sanitary Engineering Svo, 2 00 

Nagle's Manual for Railroad Engineers 16mo, morocco, 3 00 

Patton's Civil Engineering .Svo, 7 50 

" Foundations... Svo, 5 00 

Pratt and Aldeu's Street-railway Road-beds Svo, 2 00 

Rockwell's Roads and Pavements in France 12mo, 1 25 

Ruffner's Non-tidal Rivers= Svo, 1 25 

Searles's Field Engineering 16mo, morocco flaps, 3 00 

" Railroad Spiral 16mo, morocco flaps, 1 50 

Siebert and Biggin's Modern Stone Cutting and Masonry. . .Svo, 1 50 

Smart's Engineering Laboratory Practice 12mo, 2 50 

Smith's Wire Manufacture and Uses Small 4to, 3 00 

Spalding's Roads and Pavements 12mo, 2 00 

8 



Spalding's HydiauMc Cement 12mo, $2 00 

Taylor's Prismoidal Formulas and Earthwork 8vo, 1 50 

Thurston's Materials of Construction, 8vo, 5 00 

* Trautwine's Civil Engineer's Pocket-book. ..16mo, mor. flaps, 5 00 

* " Cross-section Sheet, 25 

* " Excavations and Embankments 8vo, 2 00 

* " Laying Out Curves 12mo, morocco, 2 50 

Waddell's De Pontibus (A Pocket-book for Bridge Engineers). 

16mo, morocco, 3 00 

Wait's Engineering and Architectural Jurisprudence Svo, 6 00 

Sheep, 6 50 

" Law of Field Operation in Engineering, etc Svo. 

Warren's Stereotomy — Stone-cutting Svo, 2 50 

Webb's Engineering Instruments 16mo, morocco, 1 00 

Wegmann's Construction of Masonry Dams 4to, 5 00 

Wellington's Location of Railways. . . Svo, 5 00 

Wheeler's Civil Engineering. Svo, 4 00 

Wolff's Windmill as a Prime Mover Svo, 3 00 



HYDRAULICS. 

Water-wheels — Windmills — Service Pipe — Drainage, Etc. 

{See also Engineering, p. 7.) 

Bazin's Experiments upon the Contraction of the Liquid Vein. 

(Trautwine.) Svo, 2 00 

Bovey's Treatise on Hydraulics. Svo, 4 00 

Coffin's Graphical Solution of Hydraulic Problems 12mo, 2 50 

Ferrel's Treatise on the Winds, Cyclones, and Tornadoes. . .Svo, 4 00 

Fuertes's Water and Public Health 12mo, 1 50 

Ganguillet & Kutter's Flow of Water. (Hering & Trautwine.) 

Svo, 4 00 

Hazeu's Filtration of Public Water Supply Svo, 2 00 

Herschel's 115 Experiments. Svo, 3 00 

Kiersted's Sewage Disposal 12mo, 1 25 

Mason's Water Supply Svo, 5 00 

Merrimau's Treatise on Hydraulics. . Svo, 4 00 

Nichols's Water Supply (Chemical and Sanitary) Svo, 2 50 

Ruffner's Improvement for Non-tidal Rivers Svo, 1 25 

Wegmann's Water Supply of the City of New York 4to, 10 00 

Weisbach's Hydraulics. (Du Bois.) Svo, 5 00 

Wilson's Irrigation Engineering Svo, 4 00 

" Hydraulic and Placer Mining 12mo, 2 00 

Wolff's Windmill as a Prime Mover Svo, 3 00 

Wood's Theory of Turbines Svo. 2 50 

9 



MANUFACTURES. 

BoiLEKS— Explosives— Iron— Sugar — Watches —Woollens, Etc. 

Alleo's Tables for Iron Analysis 8vo, $3 00 

Beaumont's Woollen and Worsted Manufacture 12mo, 1 50 

Bolland's Encyclopaedia of Founding Terms 12mo, 3 00 

The Iron Founder 12mo, 3 50 

" " " " Supplement 12mo, 2 50 

Bouvier's Handbook on Oil Painting 12mo, 2 00 

Eissler's Explosives, Nitroglycerine and Dynamite 8vo, 4 00 

Ford's Boiler Making for Boiler Makers: 18mo, 1 00 

Metcalfe's Cost of Manufactures 8vo, 5 00 

Metcalf 's Steel— A Manual for Steel Users. 12mo, 2 00 

* Reisig's Guide to Piece Dyeing 8vo, 25 00 

Spencer's Sugar Manufacturer's Handbook. . . .16mo, mor. flap, 2 00 
" Handbook for Chemists of Beet Sugar Houses. 

16mo, mor. flap, 3 00 

Thurston's Manual of Steam Boilers 8vo, 5 00 

Walke's Lectures on Explosives 8vo, 4 00 

West's American Foundry Practice 12mo, 2 50 

" Moulder's Text-book 12mo, 2 50 

Wieclimanu's Sugar Analysis Small 8vo, 2 50 

Woodbury's Fire Protection of Mills 8vo, 2 50 

MATERIALS OF ENGINEERING. 

Strength — Elasticity — Resistance, Etc. 
{See also Engineering, p. 7.) 

Baker's Masonry Construction 8vo, 

Beardslee and Kent's Strength of Wrought Iron 8vo, 

Bovey's Strength of Materials 8vo, 

Burr's Elasticity and Resistance of Materials 8vo, 

Byrne's Highway Construction 8vo, 

Church's Mechanics of Engineering — Solids and Fluids 8vo, 

Du Bois's Stresses in Framed Structures Small 4to, 

Johnson's Materials of Construction 8vo, 

Lanza's Applied Mechanics 8vo, 

Martens's Materials. (Henning.) 8vo. {In the press.) 

Merrill's Stones for Building and Decoration 8vo, 

Merriman's Mechanics of Materials 8vo, 

" Strength of Materials 12mo, 

Pattou's Treatise on Foundations 8vo, 

Rockwell's Roads and Pavements in France 12mo, 

Spalding's Roads and Pavements ]2mo, 2 00 

10 



5 00 


1 50 


7 50 


5 00 


5 00 


6 00 


.0 00 


6 00 


7 50 


5 00 


4 00 


1 00 


5 00 


1 25 



Thurston's Materials of Constructiou 8vo, $5 00 

" Materials of Eugiueering 3vols.,8vo, 8 00 

Vol. I., Nou-metallic 8vo, 3 00 

Vol. II., Iron aud Steel 8vo, 3 50 

Vol. III., Alloys, Brasses, and Bronzes 8vo, 2 50 

Wood's Resistance of Materials 8vo, 2 00 

MATHEMATICS. 

Calculus— Geometry — Tkigonometet, Etc. 

Baker's Elliptic Functions Svo, 

Ballard's Pyramid Problem Svo, 

Barnard's Pyramid Problem 8vo, 

Bass's Differential Calculus 12mo, 

Briggs's Plane Analytical Geometrj' 12mo, 

Chapman's Theory of Equations 12mo, 

Compton's Logarithmic Computations 12mo, 

Davis's Introduction to the Logic of Algebra Svo, 

Halsted's Elements of Geometry ...Svo, 

" Synthetic Geometry Svo, 

Johnson's Curve Tracing 12mo, 

" Differential Equations — Ordinary and Partial. 

Small Svo, 

" Integral Calculus 12mo, 

" " " Unabridged. 12mo. {In the press.) 

" Least Squares , 12mo, 1 50 

Ludlow's Logarithmic and Other Tables. (Bass.) Svo, 2 00 

" Trigonometry with Tables. (Bass.) ...Svo, 

Mahnn's Descriptive Geometr}'- (Stone Cutting) Svo, 

Merriman and Woodward's Higher Mathematics Svo, 

Merriman's Method of Least Squares Svo, 

Parker's Quadrature of the Circle Svo, 

Rice and Johnson's Differential and Integral Calculus, 

2 vols, in 1, 12mo, 

" Differential Calculus Small Svo, 

" Abridgment of Differential Calculus. 

Small Svo, 

Totten's Metrology Svo, 

Warren's Descriptive Geometry 2 vols., Svo, 

' ' Drafting Instruments 12mo, 

" Free-hand Drawing 12mo, 

" Higher Linear Perspective Svo, 

" Linear Perspective 12mo, 

" Primary Geometry 12mo, 

" Plane Problems 12mo, 

11 





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4 00 




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50 




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75 




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5 00 


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2 50 


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Warren's Problems and Theorems 8vo, $2 50 

" Projection Drawing 12mo, 150 

Wood's Co-ordiuate Geometry 8vo, 3 00 

" Trigonometry 12mo, 100 

Woolf s Descriptive Geometry Royal 8vo, 3 00 

MECHANICS-MACHINERY. 

Text-books and Practical Works. 
{See also Engineering, p. 7.) 

Baldwin's Steam Heating for Buildings 12mo, 2 50 

Benjamin's Wrinkles and Recipes 12mo, 2 00 

Chordal's Letters to Mechanics 12mo, 2 00 

Church's Mechanics of Engineering. Svo, 6 00 

" Notes and Examples in Mechanics Svo, 2 00 

Crehore's Mechanics of the Girder Svo, 5 00 

Cromwell's Belts and Pulleys -12mo, 1 50 

" Toothed Gearing 12mo, 1 50 

Compton's First Lessons in Metal Working 12mo, 1 50 

Compton and De Groodt's Speed Lathe 12mo, 1 50 

Dana's Elementary Mechanics 12mo, 1 50 

Dingey's Machinery Pattern Making 12mo, 2 00 

Dredge's Trans. Exhibits Building, World Exposition. 

4to, half morocco, 10 00 

Du Bois's Mechanics. Vol. I., Kinematics Svo, 3 50 

Vol. IL, Statics Svo, 4 00 

Vol. in. , Kinetics Svo, 8 50 

Fitzgerald's Boston Machinist ISmo, 1 00 

Flather's Dynamometers 12mo, 2 00 

Rope Driving 12mo, 2 00 

Hall's Car Lubrication 12mo, 1 00 

Holly's Saw Filing 16mo, 75 

Johnson's Theoretical Mechanics. An Elementary Treatise. 
{In the press. ) 

Jones's Machine Design. Part I., Kinematics Svo, 1 50 

" " " Part II. , Strength and Proportion of 

Machine Parts Svo, 

Lanza's Applied Mechanics Svo, 7 50 

MacCord's Kinematics Svo, 5 00 

Merriman's Mechanics of Materials Svo, 4 00 

Metcalfe's Cost of Manufactures Svo, 5 00 

Michie's Analytical Mechanics Svo, 4 00 

Richards's Compressed Air 12mo, 1 50 

Robinson's Principles of Mechanism Svo, 3 00 

Smith's Press-working of Metals Svo, 3 00 

Thurston's Friction and Lost Work Svo, 3 00 

12 



Thurston's The Animal as a Machine , 12mo, $1 00 

Warren's Machine Construction 3 vols., 8vo, 7 50 

Weisbach's Hydraulics and Hydraulic Motors. (Du Bois.)..8vo, 5 00 
" Mechanics of Engineering. Vol. III., Part I., 

Sec. I. (Klein.) 8vo, 5 00 

Weisbach's Mechanics of Engineering. Vol. III., Part I., 

Sec, 11. (Klein.)*. ..".,. 8vo, 5 00 

Weisbach's Steam Engines. (Du Bois.) 8vo, 5 00 

Wood's Analytical Mechanics 8vo, 3 00 

" Elementary Mechanics 12mo, 125 

" " " Supplement and Key 12mo, 1 25 

metallOrqy. 

Iron — Gold— Silver — Alloys, Etc. 

Allen's Tables for Iron Analysis 8vo, 3 00 

Egleston's Gold and Mercury Large 8vo, 7 50 

" Metallurgy of Silver Large 8vo, 7 50 

* Kerl's Metallurgy — Copper and Iron 8vo, 15 00 

* " " Steel, Fuel, etc .8vo, 15 00 

Kunhardt's Ore Dressing in Europe 8vo, 1 50 

Metcalf '3 Steel— A Manual for Steel Users. 12mo, 2 00 

O'Driscoll's Treatment of Gold Ores Svo, 2 00 

Thurston's Iron and Steel Svo, 3 50 

Alloys ...8vo, 2 50 

Wilson's Cyanide Processes 12mo, 1 50 

MINERALOGY AND MINING. 

Mike Accidents — Ventilation — Ore Dressing, Etc. 

Barringer's Miuerals of Commercial Value Oblong morocco, 2 50 

Beard's Ventilation of Mines 12mo, 2 50 

Boyd's Resources of South Western Virginia Svo, 3 00 

" Map of South Western Virginia Pocket-book form, 2 00 

Brush and Penfield's Determinative Mineralogy. New Ed. Svo, 4 00 

Chester's Catalogue of Minerals Svo, 1 25 

" " " " Paper, 50 

" Dictionary of the Names of Minerals Svo, 3 00 

Dana's American Localities of Minerals Svo, 1 00 

" Descriptive Mineralogy. (E. S.) Svo, half morocco, 12 50 

" Mineralogy and Petrography (J.D.) 12mo, 2 00 

'■' Minerals and How to Study Them. (E. S.).. 13mo, 1 50 

" Text-book of Mineralogy. (E. S.).. .New Edition. Svo, 4 00 

* Drinker's Tunnelling, Explosives, Compounds, and Rock Drills. 

4to, lialf morocco, 25 00 
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Eglestoa's Catalogue of Miuerals and Synonyms 8vo, $2 50 

Eissler's Explosives — Nitroglycerine and Dynamite 8vo, 4 00 

Hussak's Rock-forming Minerals. (Smith.) Small 8vo, 2 00 

Ihlseng's Mauiial of Mining Svo, 4 00 

Kimbardt's Ore Dressing in Europe. , Svo, 1 50 

O'Driscoll's Treatment of Gold Ores Svo, 2 00 

* Penfield's Record of Mineral Tests *. . . .Paper, Svo, 50 

Rosenbusch's Microscopical Physiography of Minerals and 

Rocks. (Iddings.) Svo, 5 00 

Sawyer's Accidents in Mines Large Svo, 7 00 

Stockbridge's Rocks and Soils Svo, 2 50 

Walke's Lectures on Explosives Svo, 4 00 

Williams's Lithology ; Svo, 3 00 

Wilson's Mine Ventilation 16mo, 125 

" Hydraulic and Placer Mining , 12mo, 2 50 

STEAM AND ELECTRICAL ENGINES, BOILERS, Etc. 

Stationaky — Marine— Locomotive — Gas Engines, Etc. 
{See also Engineering, p. 7.) 

Baldwin's Steam Heating for Buildings 12mo, 2 50 

Clerk's Gas Engine Small Svo, 4 00 

Ford's Boiler Making for Boiler Makers ISmo, 1 00 

Hemenway's Indicator Practice 12mo, 2 00 

Hoadley's Warm-blast Furnace Svo, 1 50 

Kneass's Practice and Theory of the Injector Svo, 1 50 

MacCord's Slide Valve Svo, 2 00 

Meyer's Modern Locomotive Construction 4to, 10 00 

Peabody and Miller's Steam-boilers Svo, 4 00 

Peabody's Tables of Saturated Steam Svo, 1 00 

" Thermodynamics of the Steam Engine Svo, 5 00 

" Valve Gears for the Steam Engine Svo, 2 50 

Pray's Twenty Years with the Indicator Large Svo, 2 50 

Pupin and Osterberg's Thermodynamics 12mo, 1 25 

Reagan's Steam and Electric Locomotives 12mo, 2 00 

ROntgen's Thermodynamics. (Da Bois.) Svo, 5 00 

Sinclair's Locomotive Running 12mo, 2 00 

Snowy's Steam-boiler Piactice Svo. {In the press.) 

Thurston's Boiler Explosions 12mo, 1 50 

" Engine and Boiler Trials Svo, 5 00 

" Manual of the Steam Engine. Part I., Structure 

and Theory , Svo, 6 00 

" Manual of the Steam Engine. Part II., Design, 

Construction, and Operation Svo, 6 00 

2 parts, 10 00 
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Tliurstou's Philosophy of the Steam Engine. 12mo, | 75 

*' Reflection on the Motive Power of Heat. (Caruot.) 

12mo, 

" Stationary Steam Engines 12mo, 

" Steam-boiler Construction and Operation 8vo, 

Spangler's Valve Gears , , 8vo, 

Weisbach's Steam Engine. (Du Bois.) 8vo, 

Whitham's Constructive Steam Engineering Svo, 

" Steam-engine Design Svo, 

Wilson's Steam Boilers. (Flather.) 12mo, 

Wood's Thermodynamics, Heat Motors, etc Svo, 

TABLES, WEIGHTS, AND MEASURES. 

For Actuaries, Chemists, Engineers, Mechanics— Metric 
Tables, Etc. 

Adriauce's Laboratory Calculations 12mo 

Allen's Tables for Iron Analysis .Svo 

Bixby's Graphical Computing Tables Sheet 

Comptou's Logarithms 12mo 

Crandall's Railway and Earthwork Tables Svo, 

Egleston's Weights and Measures ISmo 

Fisher's Table of Cubic Yards Cardboard 

Hudson's Excavation Tables. Vol. II Svo 

Johnson's Stadia and Earthwork Tables , Svo 

Ludlow's Logarithmic and Other Tables. (Bass.) 12mo 

Totteu's Metrology Svo 

VENTILATION. 

Steam Heating — House Inspection — Mine Ventilation. 

Baldwin's Steam Heating 12mo, 2 50 

Beard's Ventilation of Mines 12mo, 2 50 

Carpenter's Heating and Ventilating of Buildings Svo, 3 00 

Gerhard's Sanitary House Inspection Square 16mo, 1 00 

Mott's The Air We Breathe, and Ventilation 16mo, 1 00 

Reid's Ventilation of American Dwellings 12mo, 1 50 

Wilson's Mine Ventilation 16mo, 1 25 

MISCELLANEOUS PUBLICATIONS, 

Alcott's Gems, Sentiment, Language Gilt edges, 5 00 

Bailey's The New Tale of a Tub Svo, 75 

Ballard's Solution of the Pyramid Problem Svo, 1 50 

Barnard's The Metrological System of the Great Pyramid. .Svo, 1 50 

Davis's Elements of Law Svo, 2 00 

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Emmou's Geological Guide-book of the Rocky Mountains. .8vo, 

Ferrel's Ti'eatise on the Winds 8vo, 

Haines's Addresses Delivered before the Am. Ry. Assn. ..13mo. 
Mott's The Fallacy of the Present Theory of Sound. .Sq. 16mo, 

Perkins's Cornell University Oblong 4to, 

Ricketts's History of Rensselaer Polytechnic Institute 8vo, 

Rotherham's The New Testament Criticallj'^ Emphasized. 

12mo, 1 50 
" The Emphasized New Test. A new translation. 

Large Bvo, 3 00 

Totteu's An Important Question in Metrology Bvo, 2 50 

Whitehouse's Lake Mceris Paper, 25 

* Wiley's Yosemite, Alaska, and Yellowstone 4to, 3 00 

HEBREW AND CHALDEE TEXT=BOOKS. 

For Schools and Theological Seminaries. 

Gesenius's Hebrew and Chaldee Lexicon to Old Testament. 

(Tregelles.) Small 4to, half morocco, 

Green's Elementary Hebrew Grammar 12mo, 

" Grammar of the Hebrew Language (New Edition). Bvo, 

" Hebrew Chrestomathy Bvo, 

Letteris's Hebrew Bible (Massoretic Notes in English). 

Bvo, arabesque, 2 25 

MEDICAL. 

Bull's Maternal Management in Health and Disease 12mo, 1 00 

Hammarsten's Physiological Chemistry. (Maudel.). Bvo, 4 00 

Mott's Composition, Digestibility, and Nutritive Value of Food. 

Large mounted chart, 1 25 

Ruddiman's Incompatibilities in Prescriptions Bvo, 2 00 

Steel's Treatise on the Diseases of the Ox Bvo, 6 00 

" Treatise on the Diseases of the Dog Bvo, 3 50 

WoodhuU's Military Hygiene , 16mo, 1 50 

Worcester's Small Hospitals — Establishment and Maintenance, 
including Atkinson's Suggestions for Hospital Archi- 
tecture 12mo, 1 25 

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